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Mr. Arthur Burrows lets a blind man hear the light of a match. Author on left. 











IN this book the reader will find the first connected 
account of the properties and applications of a 
chemical element which has raised and disappointed 
more hopes than any other element known. Selen- 
ium is now just coming into its own, and it promises 
to have a paramount influence upon wireless and other 
new developments of the present century. On the 
eve of the new year. Sir Oliver Lodge addressed a 
great meeting of wireless devotees. He concluded 
by saying : 

fe We are living in an extraordinary time. The 
first twenty-three years of this century have started 
out remarkably, and what may be going to come in 
the next twenty-three years during which you will 
live and work, who can say 1 I only know that the 
amount of things to be found out in the universe is 
enormous ; more than what we have found out. "We 
live in a most mysterious and wonderful time, and 
it is our privilege to find out and harness and use our 
discoveries for the benefit of man." 

Sir Oliver Lodge was closely connected with at 
least one of the operations of selenium described in 


this work, but few are the people who realise what it 
means to " harness our discoveries for the benefit 
of man/' and how such harnessing may depend for 
its success upon the action of a few public-spirited 


February, 1924. 






















FILM 154 

APPENDIX . . . - - .160 
INDEX .... 165 


THE EXPLORING OPTOPHONE, 1912 . frontispiece 


1. CHARGE BY INDUCTION. . . . .21 




5. SELENIUM CONTROL . . . Facing 66 

6. THE " DAWN " 68 


8. INTERMITTENT LIGHT . . . Facing 66 


10. TONOGRAM (F) Facing 92 

11. TONOGRAM (B FLAT) .... 3 , 92 




15. BEADING OPTOPHONE, 1913 .... 105 
ISA. THE SAME .... Facing 98 


17. DETAILS OF OPTOPHONE, 1918 . Facing 124 


OPTOPHONE ...... 126 




17c. OPTOPHONE Disc ..... 127 









27. READING METHOD ..... 141 

28. READING METHOD (" GBAPHIC ") . Facing 124 

29. Miss JAMESON AT LIVERPOOL . ,, 68 







THE mythology of Ancient Greece that unsur- 
passed apotheosis of the human race tells us that in 
the beginning there existed Uranos and Gaea, Heaven 
and Earth. From their mystic union sprang 
Hyperion, the Titan or super-man, the eternal rebel 
against Fate. And it was Hyperion who became the 
Father of Light. His beautiful children, Helios, the 
Sun ; Selene, the Moon ; and Eos, the Dawn, came 
to gladden k the world for ever with their precious 
gifts of illumination. 

It is fitting that the name of another great agent 
in natural phenomena should be derived from the 
Greek. Electricity is the amber-force, which to the 
Greek mind resided in that precious yellow jewel 
from the Baltic, more valuable than gold, which 
the Greeks called " Electron." 

And these two great agents, Light and Electricity, 
are linked together by an element nmaed after the 



Shining One who, in her silver chariot drawn by 
white horses, drives nightly across the star-strewn 

The beautiful fancies of Ancient Greece have 
faded away into the realm of the ideal before the 
dry light of modern science. And yet, who shall say 
that our present-day conceptions are more " real " 
and less fanciful than those of the Greeks ? We 
speak of light as consisting of vibrations of an all- 
pervading yet intangible substance, a substance 
which has consistently eluded all our efforts to prove 
its actual existence. Like the Greek gods, the ether 
indicates its existence by its actions. Zeus reveals 
himself in his thunder, and the ether manifests itself 
in the vibrations which constitute light. The frontier 
between knowledge and imagination has not been 
pushed back very far ! 

The nature of electricity is, if anything, still more 
mysterious. We " know " by this time that it con- 
sists of two sorts of electric atoms, the " negative " 
ones being called " electrons," and the " positive " 
ones being called " protons. 3 ' The electrons produce 
most of the electrical phenomena accessible to our 
senses. Present-day science is disposed to assume 
that all matter consists of different aggregations or 
arrangements of these protons and electrons, which 
play the part of the elementary particles called 
" atoms " by the great Greek philosopher Demo- 
critus. And so we arrive at the dictum that 
electricity is the basis of all matter. Such a dictum 


removes tlie final mystery one stage farther back, 
and leaves us face to face with the question : What 
is Electricity ? Whatever it may be, it presents a 
dualism such as confronts us in the organic world 
through the contrast between an active and mobile 
male sex and a passive, receptive, and more or less 
stationary female sex, the former being typical of 
the negative electrons and the latter of the positive 
protons. It would not be altogether surprising to 
find some audacious philosopher of the future describ- 
ing the two kinds of electricity as consisting of living 
beings of sub-atomic dimensions, divided, like the 
higher animalcules, into two sexes, and living their 
life on a scale of time and space removed a millionf old 
from the latter. In that case the ultimate laws of 
nature would be laws of life instead of being laws of 
" dead matter/' and a tremendous step would be 
achieved towards the unification of our philosophic 

But that time is not yet, and we must leave the 
elucidation of the ultimate nature of electricity to 
the future. We must take the proton and the electron 
for granted, and endeavour to account for electrical 
phenomena by their various combinations and relative 

Ordinary matter we must imagine as consisting of 
protons and electrons in equal numbers. Any portion 
of matter containing an excess of protons will be 
"positively charged/' and any portion of matter 
containing an excess of electrons will be " negatively 


charged." Thus, if we rub a stick of sealing-wax 
on fur, the sealing-wax will deprive the fur of some 
of its electrons. The fur will be positive, and the 
sealing-wax will become negatively charged. The 
two oppositely charged bodies will attract each other, 
as do the protons and electrons themselves. The 
hairs of the fur will point towards the sealing- 

Could we but enlarge a piece of the sealing-wax 
a hundred millionfold, we should see a structure of 
indescribable grandeur and beauty. We should see 
untold numbers of three-sided pyramids the carbon 
atoms interspersed with hydrogen atoms, each con- 
sisting of one proton accompanied by one electron 
revolving round it, like a planet round the sun. 
Then there would be the nitrogen atoms, each con- 
taining fourteen protons, nine of which are locked 
up in the centre with nine electrons to match them, 
while the other protons and electrons are more or 
less loosely attached to the triangular nucleus. The 
oxygen atoms would look like octahedral diamonds. 
Then there would be the more complicated mercury 
and sulphur atoms constituting the vermilion which 
gives the sealing-wax its red colour. All this array 
of atoms would be seen arranged in groups and 
subgroups and larger aggregations, and in and out 
among them would be seen to dart a few free electrons, 
ready to follow any electric forces acting from outside, 
and constituting what little " electric conductivity " 
is possessed by a high insulator like sealing-wax. 


Waves of light, some fifty thousand of winch go 
to the inch, would appear very large compared with 
the atoms constituting the sealing-wax, and would, 
in fact, surpass the diameter of atoms several thousand 
times. It is only when we come to ether waves of 
the shortest length, those known as X-rays and 
Gamma-rays respectively, that we find anything like 
the small dimensions of the atoms themselves. 

The late Lord Kelvin used to illustrate the size 
of atoms, or rather of those simple combinations of 
different atoms called " molecules/' by saying that 
if a drop of water were magnified to the size of the 
earth, the molecules of the water would appear as 
large as cricket balls. They would be sufficiently 
fkr apart to move about freely, like a loosely packed 
crowd. But the molecules would not in the least 
resemble cricket balls in appearance. They would 
appear as clusters of atoms, and each atom would 
be a sort of solar system consisting of a closely packed 
nucleus surrounded by revolving electrons. The 
latter would fill up no more space within the " atom " 
than do the planets, comparatively speaking, in the 
solar system of our sun. If the atom were the size 
of a cricket ball, the electrons would be smaller than 
pins' heads. But small as they are, they are packed 
with material of what is to us an inconceivable density, 
so that their mass-effect is quite considerable so 
considerable, in fact, that they are capable of melting 
platinum by the force of their impact. The electron 


in motion is the most terribly effective projectile 

Let us endeavour to form a mental image of the 
forms of matter as we know them, enlarged sufficiently 
to show their atpmic structure. The simplest form 
of matter will be a gas, say oxygen or nitrogen, or that 
mixture of both which we call Air. Let us enlarge 
the sample of air so that its new diameter is one 
hundred million times its former diameter, and let 
us, at the same time, reduce the tremendous speeds 
of atoms and electrons in the same proportion. Then 
what shall we find ? 

Each molecule of air will be about an inch across. 
It will be a sort of twin star, consisting of two atoms 
with their attendant electrons. The molecules will 
be some 10 inches apart on the average, but they 
wiR be found to be in constant motion, like a swarm 
of midges, covering about half an inch per hour on 
the average. Each molecule will move in a straight 
line until it encounters another molecule. It will 
do this after traversing, on the average, a distance 
of 30 feet, so that each molecule will collide with 
another about once per week. Such a collision will 
disturb the equilibrium of both molecules, and it will 
happen occasionally that an electron will leave one 
molecule and take up a temporary abode with the 
other. This is not surprising if we consider that 
the (new) speed of the outermost electrons will 
be about half an inch per second, or about a 


thousand times greater than the speed of the 

When such an exchange of electrons takes place, 
the molecules will no longer be electrically neutral, 
but will be "electrically charged/' The molecule 
which has lost an electron will have a "positive 
charge/' while the molecule which has captured it 
will have a " negative charge/' These charges force 
the two molecules (which are now called " ions ") to 
obey any electric force which may be acting upon 
the gas from outside. The gas becomes to some 
extent "ionised/' or converted into "ions." (We 
shall see later how lig^t ionises selenium.) In time, 
all the molecules of the gas would be ionised by 
collision, but for the fact that the two sorts of ions 
attract each other and approach sufficiently to allow 
the errant electron to return to its former allegiance. 
In the long-run, a state of equilibrium is attained, 
in which there is a permanent residue of ions in a 
large volume of gas. 

Now let us imagine the gas condensed into a liquid. 
The molecules will be in actual contact, but it will 
be a loose contact which allows them to glide about 
among each other, like a sea-side crowd in a popular 
resort. The molecules will form larger aggregations, 
and if there are any strange molecules among them, or 
powerful ions, each of these will collect round it, or 
drag about with it, a retinue of neutral molecules, 
much as a show or a procession does in a crowd. If 


an electric force acts upon the liquid from outside, 
a migration of the ions will set in. They will slowly 
drag ; themselves through the jostling crowd of mole- 
cules in obedience to the call, and will communicate 
their charges to the metallic " electrodes " from which 
the force is exerted. We shall have, in fact, what is 
known as " electrolysis/' 

Finally, let us consider the molecules condensed into 
a solid. As most ordinary gases are difficult to 
solidify, we must imagine the solid compound of other 
atoms, say those of copper or sulphur. Those of 
copper will each contain twice as many protons and 
electrons as those of sulphur, and each copper atom 
will therefore weigh as much as two sulphur atoms. 
But in addition to this, the copper atoms will be 
more closely packed, so that a given volume of 
copper contains more than twice as many copper 
atoms as the same volume of sulphur contains of. 
sulphur atoms. It is, therefore, not surprising that 
the electrons which are loosely associated with the 
copper atoms those which revolve in the outer 
orbits of the atom are comparatively easily detached 
and allowed to roam freely through the substance of 
the copper. The atom of sulphur, on the other 
hand, is so constituted that it can absorb one or two 
extra electrons with comparative ease and keep them 
in a state of permanent attachment. And so we find 
that while a lump of copper contains very many 
unattached electrons, a lump of sulphur contains 


very few indeed. In other words, copper is a " good 
conductor " of electricity, while sulphur is a very bad 
one in other words, it is an excellent " insulator/' 

If we rub the lump of sulphur with wool or fur, 
it will absorb electrons from them, and will thus 
become " negatively charged." The fur, having lost 
electrons, will become " positively charged." Now 
let us separate the fur from the sulphur and place 


between them our lump of copper. The free electrons, 
being repelled by all other electrons, will tend to 
move away from the " negative charge " of the 
sulphur, and will be attracted by the " positive 
charge " (the unbalanced protons) of the fur. One 
end of the copper will thus acquire a negative charge, 
while the other end the end from which the electrons 
have fled will be " positively charged." This pro- 
cess is known as " charge by induction." 

It would be quite feasible to divide the copper in 


the middle, and so obtain two pieces, one being 
" negatively " and the other " positively " charged. 
If we then remove the sulphur and the fur, the 
electrons in the " negative " copper will tend to 
return to their natural allegiance and alliance with 
the unmatched protons in the " positive " copper. 
They find it, however, very difficult to emerge from 
copper unless it is heated to a red heat, and so they 
will take up their positions as near to the " positive " 
copper as they can. Such a combination of two 
oppositely charged conductors is called a " condenser," 
because it allows us to accumulate a considerable 
electric charge and to store it for some time. It can 
be liberated by separating the two conductors. If 
we thus take the piece of copper containing the super- 
numerary electrons and let it touch an uncharged 
piece of copper, the free electrons will distribute 
themselves over the two pieces. The new piece will 
thus be " charged by contact." It can be discharged 
by allowing it to touch a large conductor, which will 
deprive it of most of its spare electrons. 

Such, briefly, is the modern view of what has been 
known for a century as " electrostatic " charge. 
What is the corresponding view of an electric current ? 

Imagine a row of copper balls placed close together. 
Charge the first of them by contact and let it share 
its electronic charge with the next. Let the latter 
share its charge with the next until some of the spare 
electrons are distributed over the whole row. Then 


it is obvious that there lias been a procession of elec- 
trons from the first to tlie last ball. On joining the 
last ball to a water pipe it will lose all its spare 
electrons, and if all the balls are in contact the whole 
battalion of unattached electrons will pass into the 

Now it is quite feasible to repeat this process in- 
definitely, so that there is a steady flow of electrons 
through the metal to the earth. That flow constitutes 
an electric current. All currents in metals are but 
a procession of electrons wending their way through 
the crowds of atoms, knocking up against them, being 
absorbed and again set free, but continuing steadily 
towards the goal set for them by the electric field of 
force in which they are placed. 

The flow will be the more copious the greater the 
number of free electrons. That is why it is more 
copious in copper than in most other metals, and why 
it is so very meagre in sulphur and other insulators. It 
will also be greater the current will be " stronger *' 
the more rapidly and smoothly the electrons can 
proceed on their way. If there is no obstacle at all 
(in a vacuum, for instance), a thin stream of electrons 
flowing at a great rate may constitute quite a con- 
siderable current. But any opposition encountered 
by the electrons increases the " resistance " of the 
substance, and the resistance can be measured by the 
heat evolved by the stoppages and collisions. If, in 
spite of the resistance, we force up the current until 
it is doubled, not only will the number of electrons 


traversing the conductor in a given time be doubled, 
but the rate at which each electron does its work in 
overcoming resistance will be doubled also. Thus the 
amount of heat developed will be increased fourfold. 
We may put these rules concisely into words as 
follows : (1) The current is proportional to the electric 
force (" electromotive force/' " E.M.F.," or voltage) 
and to the conductivity (Ohm's Law). (2) The 
heating effect is proportional to the square of the 
current (Joule's Law). 

There is a fundamental law of motion, first formu- 
lated by Newton, and called Newton's Third Law. It 
maintains that " Action and Eeaction are always 
equal and opposite." In other words, if a body is 
set in motion by a force acting between it and another 
body, the amount of motion, or rather " momentum " 
(mass multiplied by speed), in both directions is 
equal. We cannot jump off the ground without 
pushing the Earth away from us by a certain amount 
an infinitesimal amount, indeed, but for all that 
an amount suitable to the disproportion between our 
own mass and that of the Earth. 

A somewhat similar thing happens in the domain 
of electricity. We cannot set electricity in motion, 
nor can we start a body of ions or electrons in any 
direction, without starting other electrons in the 
opposite direction. It is just as if every electron were 
connected with every other by invisible elastic fibres, 
so that none of them could start in any direction 


without the help of all the rest. Supposing we had 
a rod of copper containing an excess of electrons, and 
that we suddenly moved it in the direction of its 
length. Then in any neighbouring copper rod 
parallel to it electrons would start in the opposite 
direction. This flow would, however, only proceed 
so long as the speed of the charged rod was increasing. 
A uniform displacement produces no effect. On stop- 
ping the charged rod, the electrons in the other would 
rush forward into their former places. This pheno- 
menon is known as electromagnetic induction or 
current induction. We can, in fact, temporarily 
" induce " a current in a coil of wire by starting or 
stopping a current in a neighbouring coil. The 
closer the neighbourhood, the stronger will be the 
effect, so that we can produce an induction effect 
by merely bringing a coil bearing a steady current 
near another coil at rest, or removing it away from 
it. If two wires or coils bearing currents in the same 
direction are brought close to each other, they will 
mutually reduce their currents during approach, and 
increase them during removal. 

There is a certain inertia or persistence which 
opposes the starting or stopping of a current in a 
conductor, quite apart from the "resistance" of 
the conductor to a steady current. This inertia 
recalls Newton's First Law of Motion, according to 
which a body, once started, tends to proceed uni- 
formly in a straight line unless and until it is stopped 
or deviated by a force applied to it. 


The induction of currents is but an illustration of 
this general law. For if, in order to start a current 
in one conductor, we must start other currents in 
all neighbouring conductors, the work of starting 
must be considerably increased. This difficulty is 
also presented by the turns of a single coil, each turn 
acting as a drag upon its 'neighbours. Such a form 
of electric inertia is called self-induction or simply 
" inductance " a term with which all wireless 
devotees are familiar. 

The influences thus exerted " across space " are 
not propagated instantaneously, but with a limited 
though very great speed, and this fact irresistibly 
suggests that there must be a medium through which 
they are propagated, a medium whose properties 
determine that speed of propagation. This hypo- 
thetical medium is called "the ether of space/'' 
Every movement of an electric charge, whether it 
consists of electrons, protons, larger ions, or charged 
bodies, sets up some sort of " strain " in the ether, 
which is propagated in all directions with the speed 
of light. It is this strain which is supposed to produce 
those movements of electricity in neighbouring con- 
ductors which we call induced currents. It is also 
manifested in the forces acting between conductors 
which are already conveying currents. These forces 
always act in the sense of placing the currents so that 
they are parallel and in the same direction (" electro- 
dynamic action ") . The most remarkable instance 
of this action is the magnetisation of a piece of soft 


iron by a current traversing a coil wrapped round the 
iron, as in an electric bell. 

What happens in this case may be described as 
follows. The atoms of the iron, like all other atoms, 
have a number of electrons revolving round their 
nuclei in circular or elliptical orbits. But in iron 
these orbits are more or less in one plane, like the 
orbits of the planets of our solar system. Now when 
a current circulates in the wire round the iron, all 
these electronic orbits tend to set themselves in 
such a manner that their electrons circulate in the 
same sense as the electrons in the wire. When that 
happens, the iron is said to be " magnetised/* What 
we call magnetism is, in fact, nothing but the action 
of the tiny atomic currents upon each other or upon 
currents in ordinary conductors in obedience to the 
laws of electrodynamic action. Every electron or 
other electric charge in motion exerts magnetic force, 
and the electrons revolving in atomic orbits are 
no exception to this rule. 

When, instead of the steady rotation of electric 
charges, we have their starting and stopping, their 
acceleration and retardation, their surging up and 
down or to and fro, we get, not magnetism, but 
radiation. Electromagnetic waves are produced in 
the ether, and are propagated through space with 
the velocity of light. The speed of light being 
300,000 kilometres (186,000 miles) per second, it is 
easy to calculate the length of these waves if we 
know the frequency with whicli the surgings at the 


source take place. If there is one to-and-fro move- 
ment per second which might be produced by 
separating the two charged pieces of copper (p. 21) 
and approaching them again the length of the wave 
will be 300,000 kilometres. With a frequency of 
a million per second we should get a wave-length 
of 300 metres, which is not far from the wave-lengths 
currently used for " broadcasting/' Increasing the 
frequency another millionf old, we should get a wave- 
length of one-thirty-third of a centimetre, or small 
waves eighty-four of which would go to the inch. 
We should have to increase the frequency another 
five hundred times to produce light-waves. We should 
then have red light, with waves so short that forty- two 
thousand of them went to the inch. 

We cannot, of course, produce several billion 
electric displacements per second mechanically. Nor 
is it, indeed, known as yet how they are produced in 
nature. The sun and other sources of light produce 
them in abundance, and it was thought for some 
time that we must seek their origin in those atomic 
circuits or electronic orbits which determine the 
phenomena of magnetism. But a magnet does not 
radiate light, whereas all ordinary bodies when raised 
to a certain high temperature do. The theory of 
radiation is just at present in one of those critical 
stages which often precedes discoveries of far-reaching 
importance. It is safe to say, however, that an 
atom does not radiate light except in a certain state 
of transition from one state of equilibrium to another. 


It may be that an electronic orbit breaks down, as 
coinetary orbits sometimes do, and the electron 
finds another orbit nearer the nucleus. While passing 
from one to the other, the electron sends out its 
S.O.S. message as a thrill through the ether of 
space, and we receive it as a flash of light. 

Another peculiarity of light radiation which is 
now definitely established is that it is transferred in 
definite quantities or "quanta/" Each quantum 
or parcel of light is the greater the more rapid the 
vibration. 1 

There is probably some connection between this 
peculiar law and the position of the electronic orbits 
in the atom. Just as in the solar system, the inner 
electrons veritable planets revolving round the 
central nucleus have much shorter periods than the 
outer ones. They are also in a more intense field 
of force, and any change probably takes place with 
explosive violence. Hence it is the high-frequency 
radiations which have the greatest intensity. 

Our eyes are sensitive to but a very limited 
range of electric waves. There are waves flooding 
space waves of invisible light which our eyes are 
unable to perceive. The sun sends out waves longer 
than those of red light. We can only perceive them 
through our sense of heat. It also emits waves 
shorter than those of violet light. We call them 

1 This is Planck's " quantum," the value of which is n X 6-55 X 1C 27 
erg for a frequency of n vibrations per second. For the brightest sun- 
light the quantum is 3-8 billionths of an erg. 


ultra-violet, and receive them on photographic plates, 
which are very sensitive to them. The ear is sensitive 
to ten or eleven octaves of the scale of notes. The 
eye does not cover even one octave of light waves. 
But it is a marvellous instrument all the same, con- 
sisting of a hundred million separate receivers dis- 
tributed over the sensitive surface called the retina. 
These receivers are affected by light in a chemical 
sense, a delicate substance called the " visual purple " 
being decomposed by light and rapidly re-formed in 
darkness. Many ocular phenomena, such as Blinding 
or dazzling, fatigue, and after-effect, are shown, as 
we shall see later, by selenium in much the same 
manner as in the eye. 

Photography has familiarised us with the chemical 
possibilities of light. The action of selenium will 
show us its electrical possibilities. 

Many things may happen to a beam of light once 
it has left its source. It may fall upon a polished 
surface and be reflected, much as a sea-wave is re- 
flected from a sea-wall. It may be absorbed and 
converted into heat, like breakers on a pebbly beach, 
It may pass freely through the substance, undergoing 
some change of direction in transmission owing to 
the influence of the electrons bound up with the 
atoms of the transparent body. 

If it is absorbed it may do many different things. 
Absorbed by the eye, it produces the sensation of 
light. Absorbed by a green leaf, it evolves oxygen. 
Absorbed by a photographic plate, it reduces the 


silver bromide and produces a latent image. Ab- 
sorbed in large quantities by the skin, it darkens it 
until, in the course of many generations, it produces 
the Black Man. Absorbed by zinc or colloidal 
potassium charged with an excess of electrons, it 
enables those electrons to emerge into open space, 
and gives rise to " photo-electricity/' 

Absorbed by crystalline selenium, it produces in it 
those temporary and significant changes which it is 
the purpose of this work to describe and investigate. 



THE discoverer of selenium, Jons Jakob Berzelius, 
who was professor of chemistry at Stockholm and 
Secretary of the Swedish Academy of Sciences, gave 
the following account of his discovery : 

" This body was discovered in 1817 in the following 
manner : I was examining, together with J. G. 
Gahn, the method formerly in use at Gripsholm for 
preparing sulphuric acid. We found in that acid a 
sediment, partly red and partly light brown, which 
before the blow-pipe gave an odour of rotten radish 
and left a grain of lead. That odour had been 
described by Klaproth as indicating the presence of 
tellurium. Gahn remembered that he had often 
noticed the smell of tellurium in places where the 
copper ore of Fahlun was worked, yielding the sulphur 
employed in the manufacture of the acid. The hope 
of finding such a rare metal in this brown sediment 
induced me to examine it. In undertaking this 
research, my only object was to separate the tel- 
lurium, but I found it impossible to discover that 
body in the material I examined. I therefore caused 
the whole of the sulphuric acid deposits to be collected, 
using nothing but Fahlun sulphur, and after collecting 
a large quantity I examined it in detail. I then 
discovered an unknown substance with properties 



closely resembling those of tellurium. THs resem- 
blance induced me to call it Selenium, from the 
Greek word SeXTp/j, which signifies the Moon, while 
Tellus is the name of our own planet/* 

For over fifty years the new element remained 
little but a chemical curiosity. It was found that 
its atom weighed 79-2 times as much as the hydrogen 
atom, that it melted at 217 Centigrade and boiled 
at 690 ; that it occurred in several " allotropic " 
modifications, the lightest of which weighed 4-3 times 
its own bulk of water ; that it was insoluble in water, 
but dissolved readily in acetone, aniline, and other 
organic liquids ; that it was allied to sulphur, a non- 
metal, on the one hand, and to tellurium, a metal, 
on the other, being itself practically non-metallic ; 
that it occurred, combined with sulphur, in Swedish 
pyrites ; that, when burned in air, it gave off an 
unpleasant smell of rotten horse-radish, and formed 
a- white oxide, which in water became selenious acid 
(SeH 2 3 ) ; that with chlorine it formed a brown oily 
liquid capable of dissolving crystallised selenium. 

But none of these properties were of any interest 
outside a text-book of chemistry. The great property 
of selenium, that of becoming a conductor of elec- 
tricity when illuminated, was not discovered until 
1873. The discovery was made at the Transatlantic 
Cable Station on Valentia Island, off the coast of 
Kerry, in the course of some experiments in cable 
signalling for submarine telegraphy. 

Here follows the full account of this momentous 


discovery, as given in a communication made by 
Mr. Willoughby Smith, Electrician of the Telegraph 
Construction Company, to the Society of Telegraph 
Engineers in London on February 12, 1873. The 
communication was presented by Mr. Latimer Clark, 
and was first published in .Nature of February 20, 
1873 : 

" Being desirous of obtaining a more suitable high 
resistance for use at the Shore Station in connection 
with my system of testing and signalling during 
the submersion of long submarine cables, I was 
induced to experiment with bars of selenium, a known 
metal of very high resistance. I obtained several 
bars varying in length from 5 to 10 centimetres, 
and of a diameter of 1 to 1^ millimetres. Each bar 
was hermetically sealed in a glass tube, and a platinum 
wire projected fiom each end for the purpose of 

The early experiments did not place the selenium 
in a very favourable light, for the purpose required, 
for although the resistance was all that could be 
desired some of the bars giving 1,400 megohms 
absolute yet there was a great discrepancy in the 
tests, and seldom did different operators obtain the- 
same result. While investigating the cause of such 
great differences in the resistance of the bars, it was 
found that the resistance altered materially according 
to the intensity of light to which it was subjected. 
When the bars were fixed in a box with a sliding 
cover, so as to exclude all light, their resistance was 
at its highest, and remained very constant, fulfilling 
all the conditions necessary to my requirements ; 
but immediately the cover of the box was removed, 
the conductivity increased from 15 to 100 per cent, 
according to the intensity of the light falling on the 


bar. Merely intercepting the light by passing the 
hand before an ordinary gas burner placed several 
feet from the bar increased the resistance from 15 
to 20 per cent. If the light be intercepted by rocksalt 
or by glass of various colours, the resistance varies 
according to the amount of light passing through 
the glass. 

To ensure that temperature was in no way affecting 
the experiments, one of the bars was placed in a 
trough of water so that there was about an inch of 
water for the light to pass through, but the results 
were the same ; and when a strong light from the 
ignition of a narrow band of magnesium was held 
about nine inches above the water the resistance 
immediately fell more than two-thirds, returning to 
its normal condition immediately the light was 

The announcement created a great stir among 
physicists and electricians. It also evoked criticism 
along the customary lines. Such criticism usually 
takes three forms : (1) That the phenomena alleged 
are due to some other cause ; (2) that they are not 
new ; and (3) that if both new and true, they are of 
no possible use to anybody. One well-known chemist 
wrote to Nature to say that he had attempted to 
repeat Willoughby Smith's experiment, but had not 
only been unsuccessful in obtaining his result, but 
had not succeeded in getting a current to pass through 
selenium at all. A German chemist did obtain an 
effect of light on selenium, but went to the other 
extreme and claimed to have proved that sensitive- 
ness to light was also exhibited by silver, gold, and 


indeed all other metals. But the truth, did not take 
long in getting firmly established. Professor (after- 
wards Sir) Norman Lockyer, the Editor of Nature, 
caused selenium to be studied by Commander Sale, 
R.N., who reported that thin slabs of selenium were 
sensitive to all the colours of the spectrum, but more 
especially to the visible red. Further investigations 
by W. Grylls Adams in England and W. Siemens in 
Germany fully confirmed the remarkable discovery, 
and from that day to this there has been a never- 
ending stream of contributions to the study of the 
Moon-element, an element as fascinating as any of 
the ninety-two elements in Nature's catalogue, and 
far more elusive than most. 

The development of our knowledge concerning 
selenium may be gathered from the following chrono- 
logical table : 

1817. Berzelius discovers selenium. 
1845. Biess determines its electrical conductivity. 
1851. Hittorf discovers allotropic forms of selenium. 
1856. Eegnault determines specific heat of selenium. 
1858. Matthiessen determines voltaic power of 

1869. Fizeau determines thermal expansion of 


1873. Willoughby Smith discovers the sensitiveness 

of selenium to light. 

1874. Quincke determines the refraction and absorp- 

tion coefficients of selenium. 

1875. Siemens proposes a selenium photometer. 
1878. Sabine constructs electrolytic selenium cells. 
1880. Graham Bell invents the photophone. 


1880. Perry and Ayrton propose electric vision. 

1881. Shelford Bidwell constructs new selenium cells. 
1881. Kalischer and Mercadier construct photo- 


1883. Hesehus determines laws of action of light. 
1891-93. Minchin uses selenium cells for stellar 

1896. Giltay discovers action of Roentgen rays on 


1901. Ruhmer transmits speech by means of the 

Speaking Arc. Invents the Photographo- 
phone. Transmits pictures. 

1902. Korn improves picture telegraphy with 

selenium. Ruhmer constructs cylindrical 
selenium cells. 

1905. Wulf and Lucas use selenium for the study 
of a solar eclipse. 

1907. Korn transmits pictures from Munich to 


1908. Ries discovers anomalous actions in selenium. 
1910. Ries suggests dissociation of selenium by 


1912. *Fournier d'Albe constructs first optophone. 

1913. Founder d'Albe constructs the first reading 


1914. Fournier d'Albe invents the type-reading 


1915. F. C. Browne invents the phonoptikon. 

1916. A. 0. Rankine invents the grid photophone. 

1917. H. Grindell Matthews steers boat from shore 

by searchlight. 

1918. First public reading demonstration with the 


1920. " Black-sounding " optophone constructed by 

Barr and Stroud. 

1921. Talking Films (De Forest, Rankine, Matthews, 

and others). 



Atomic Weight 79-2. 

Linear Expansion 0-000049 (crystalline). 

per degree C. 0-000037 (vitreous). 
Density 4-26 (red amorphous). 
4-28 (vitreous). 
4-47 (red crystalline). 
4-80 (grey crystalline). 
Melting Point 217 C. 
Boiling Point 690 C. 
Specific Heat 0-084 (crystalline). 
0-095 (amorphous). 
Specific Kesistance (of cm. cube) 70,000 ohms 



W. Siemens was the first to construct a " selenium 
cell" (1876). It consisted of two platinum wires 
wound in a flat double spiral and attached to a sheet 
of mica. The sheet and wires were then coated with 
molten selenium and exposed for some hours to a 
temperature of 200 C. 

Many different forms of selenium " cells " have 
been devised since that time. The object of all 
designers was to reduce the resistance as much as 
possible. For the current obtainable from a battery 
discharged through a slab of selenium was always 
excessively small. It was therefore necessary to 
widen the path of the electrons through the selenium 
and also to shorten it as much as possible. A wire 
of crystalline selenium oilers an enormous resistance 
thousands of megohms to the passage of a current. 


If the wire were made very thick the resistance would 
be less, as many electrons could pass along abreast 
of each other. If the wire were made short as well 
as thick, the conditions would be still better. But 
another requisite is that the whole of the selenium 
should be capable of exposure to light. This can 
only be secured by spreading it in a thin sheet. If 
two parallel wires were stretched out close together 
we could send a current from one wire across to the 
other over a narrow obstacle of selenium filling up 
the gap between the two. If, in addition, we roll 
the parallel wires up in a flat spiral, we obtain the 
Siemens cell described above. 

Bidwell (1880) devised a more convenient form of 
cell by cutting a series of notches in a square of 
slate and winding two wires in a spiral round 

Graham Bell (1880) used a brass plate perforated 
with numerous holes which were nearly plugged by 
corresponding cones attached to a second plate. The 
interstices were filled up with selenium. A better 
plan of the same inventor was to make cylindrical 
selenium cells by building up a cylinder consisting 
of numerous circular brass plates separated by discs 
of mica of a slightly smaller diameter. The remaining 
interstices were filled up with selenium and alternate 
brass plates were connected together to form the 
two electrodes, 

Mercadier (1881) rolled up two narrow strips of 
thin brass, separated from each other by means of 


parchment, into a spiral and covered one face of the 
spiral with selenium. 

Fritts (1883) had the novel idea of coating two 
glass plates with gold-leaf, pressing molten selenium 
into a thin layer between them, and illuminating the 
latter through the sdmi-transp'arent gold. 

Righi (1888) also used selenium discs, but pressed 
them between wire gauze. 

Liesegang (1890) produced a very simple cell by 
ruling a line across a thin layer of silver on glass and 
filling up the gap with selenium. 

Ruhmer (1902) produced cylindrical selenium cells 
by winding a double screw thread on a cylinder of 
steatite, which was wound with wire and then coated 
with selenium. 

Quite a new form of selenium cell was invented 
by Sabine in 1878. He coated a metallic plate with 
selenium on one side, while varnishing the other, and 
placed it opposite another plate in an electrolyte. 
On illumination this " electrolytic selenium cell '* 
was found to produce its own electromotive force. 
Minchin (1895) improved this type by coating the 
flat end of an aluminium wire with selenium, enclosing 
it in a glass tube open at both ends and immersing 
it in a solution of cenanthol opposite a platinum wire. 
This cell also produced an electromotive force under 
the action of light, and was used for star photometry. 

All selenium cells made with wires wound close 
together suffer from a serious defect. It is the danger 
that a small portion of selenium between two wires 


may melt with the lieat of the current, whereupon 
the two wires are likely to touch and produce a short- 
circuit, fatal to any delicate instruments which may 
be connected with the cell. This danger is avoided 
in a cell devised by Presser, who covered a circular 
slab of soapstone with platinum and ruled concentric 
grooves in it, subsequently covering the entire surface 


with a of selenium. The burning out of 

a portion of ilie selenium then only produces a slight 
increase in the resistance. 

It is best, however, that no metallic substances 
be used to make the connection with the sensitised 
selenium, as all met^ijs form selenides or compounds 
with selenium, and these compounds gradually reduce 
the sensitiveness. 



Carbon forms no such, compounds, and it can be 
very conveniently used in the form of graphite. 

The best basis is unglazed " biscuit/' sometimes 
called unglazed porcelain. But soapstone or slate 
can also be used. 

The practical method of constructing carbon- 
selenium tablets, as worked out by the author, is as 
follows : 

Cut out with a hacksaw a piece of ordinary writing 

J - 


slate of the size required say, 2 inches s'quare. 
One surface should be smoothed by ui^|s of sand- 
paper. (If two pieces of slate are prepared, the two 
surfaces should adhere for a short time if pressed 

Now cover the smooth surface with graphite by 
rubbing it over with a soft pencil. After a good 
covering is attained, rub in the graphite with a piece 
of leather and produce a good black polish. 


Next, inscribe a to-and-fro line in the graphited 
surface with, a sharp steel point, cutting just suffi- 
ciently deep to penetrate the graphite surface. The 
cut (Fig. 3) should not be more than half a millimetre 
wide (about -$ in.). 

Now comes the more difficult operation that of 
coating the surface with selenium. 

As the fumes of selenium are unpleasant, the 
coating should be done in the open air or in a well- 
ventilated place. 

Have ready two pairs of pliers, a Bunsen burner, 
a slab or block of iron, and a narrow strip of glass. 

Light the burner, and grip one corner of the slate 
in a pair of pliers. Grip a piece of selenium about 
the size of a hazel nut in the other pliers, Plunge 
the slate into the flame, moving it to and fro so as to 
get an even heat. After half a minute or so the slate 
will crackle, without actually breaking. Whip it 
out of the flame and apply the selenium as if you 
wanted to paint it on. It will probably collect into 
drops. Apply a little more heat and you will find 
a temperature at which it spreads like butter, though, 
it will then be too thick. Put down the selenium, 
bit and take up the strip of glass. With this glass, 
spread the selenium evenly over the slate with the 
exception of the ungrooved portions at each side. 
The surplus selenium will adhere to the glass. 

The above operation is difficult, but with some 
practice a smooth, even, glossy black covering of 
selenium can be obtained. Do not keep smoothing 


after the selenium lias begun to congeal, or you will 
get a purple crystalline variety which is quite 

After coating, the slate should be placed on the iron 
slab to cool quickly. 

When cold, the selenium will be quite non-con- 
ducting. If a battery and a sensitive galvanometer 
are joined to the two uncoated side strips of graphite, 
no current should be indicated. If there is a current, 
it means that the grooving is incomplete at some 



point. The zig-zag groove should be one continuous 
line dividing the graphited surface into two entirely 
separate portions. 

If no current is indicated, we may proceed to 
" anneal " the selenium. This is conveniently done 
on an iron slab \ in. thick, heated with the Bunsen 
at one end. A steady gradient of heat can thus be 
obtained, one end being nearly red-hot while the 
other can still be touched. 

The annealing consists of two operations. In the 
first operation the black lustrous selenium is con- 
verted into the grey crystalline variety by heating. 


This consists in bringing the selenium gradually 
as closely as possible up to its melting point, and 
keeping it there for at least half an hour. 

This can be done by putting it back on the former 
spot on the slab and gradually moving it up to the 
hot end. 

Selenium melts at 217 C., and on cooling returns 
to the black, glassy, non-conducting state. Such 
melting must, therefore, be carefully avoided. While 
making the slate gradually hotter, watch for the 
appearance of black spots in the grey selenium. If 
you see one forming, whip off the slate on to the cold 
slab. The black spot will then often disappear by 
re-crystallising. In any case, you will know that you 
are sufficiently near the melting-point. 

The final cooling on the cold slab must be acceler- 
ated by moving the slate about on the slab, as other- 
wise the selenium is likely to become " hygroscopic " 
and attract moisture. 

As soon as the slate is cool, it is ready for mounting 
and testing. A simple mounting is shown in Fig. 4. 
The lightest contact between metal and graphite is 
as good as the heaviest, so long as it is secure. The 
metallic leads should not touch the selenium coating. 
These graphite-selenium tablets have great stability, 
and some of them have been in use for many years 
without deterioration. 



MANY different theories have been propounded in 
order to account for the action of light on the con- 
ductivity of selenium. 

Moser (1881) supposed that the effect was due to 
heat, which improved the contact between the 
selenium and the electrodes of the cell. 

Sale (1873) propounded the theory that the 
additional conductivity is due to ether waves pene- 
trating between the selenium atoms and thus increas- 
ing the conductivity of the whole substance. In 
this case, of course, the effect should be instantaneous, 
which it is not. 

Bidwell (1885, 1895) attributed the action to the 
formation of selenides with the material of the 
electrodes. This is refuted by the fact that carbon 
electrodes, which form no selenides, give equally 
good results. 

Another hypothesis found many adherents. It is 
that there are two modifications of crystalline sele- 
nium, one of which is a good conductor, while the 
other is an inferior conductor. Ordinarily, these are 
in a state of equilibrium. But illumination upsets 



tliis equilibrium, so that more of tlie highly conducting 
variety is formed. In the dark, this formation is 
gradually reversed, and the normal resistance is 
eventually re-established. This hypothesis was 
favoured by Siemens (1876), Berndt, Biltz (1904), 
Hesehus (1906), Pfund, Marc, and F. C. Browne. 
It is, however, rendered extremely improbable by 
the fact that most of the light-sensitiveness is retained 
at very low temperatures, such as the temperature 
of liquid air ( 185 C.), whereas chemical processes 
are either very much slowed down by extreme cold 
or stopped altogether. 

Our views of conduction in solids have only become 
clear and definite since the new century began. 
We now know, thanks to the work of Sir J. J. Thom- 
son, Riecke, Drude, Stark, and many other physicists, 
that metallic conduction consists in the conveyance 
of electrons through the metal, while the conduction 
of electricity through liquids means the passage of 
" ions " or groups of atoms, under the guidance of 
unbalanced electrons or protons, in the direction 
imposed by the electric field of force. In semi- 
conductors like crystalline selenium we may suppose 
it to mean a mixture of both processes, but since 
even a prolonged exposure of selenium to a current 
shows little sign of the actual transfer of selenium 
atoms by the current, we can be pretty certain that 
what little electrical conductivity is possessed by 
selenium, or generated by light, is due to free 


While in a lump of copper there are nearly as 
many free electrons as there are atoms, the case is 
very different in a poor conductor like selenium. 
We are not likely to be far wrong in estimating that 
there is normally only one free electron to every 
billion selenium atoms. A selenium tablet 1 inch 
square will contain about a million free electrons 
among its billion selenium atoms. When intensely 
illuminated, it will contain many additional free 
electrons, perhaps ten times as many as in the dark 
In some selenium cells with large selenium crystals 
there may be a hundred times as many. 

It is our business now to consider how light affects 
the number of free electrons. For the conductivity 
is directly proportional to it, and the whole value 
of selenium lies in the fact that we can make light 
impart an electrical conductivity to it. 

It takes a certain effort to make an electron leave 
an atom with which it is bound up, in other words, 
to " ionise " the atom. This work is estimated to 
be about a ten thousand millionth of an " erg " (the 
physical unit of work). Now all light has a certain 
energy or capacity of doing work, and there is no 
reason why it should not perform the work of ionising 
the selenium atoms. A candle shining . upon our 
selenium tablet from a distance of 3 feet would 
throw upon it sufficient energy to ionise as many as 
four hundred billion atoms per second, so that if 
the process went on unchecked for an hour the whole 
of the atoms of the selenium would be ionised 


and it would acquire the conductivity of silver or 

That desirable consummation does not, however, 
take place. The conductivity of the selenium rises 
for a second or two, more and more slowly, and then 
reaches a value which remains constant for the rest 
of the time. On cutting off the light, the conductivity 
falls rapidly, though not so rapidly as It rose, and 
eventually returns to its normal value in the dark. 

There is, therefore, some quality or agency whicli 
opposes the rise of conductivity, and which neutralises 
and annuls it at the first opportunity. So far from 
being fatal to the value of selenium, it is the most 
valuable quality of all. For a single and irreversible 
action of light would be nothing new. We have 
that at our disposal in the photographic plate. In 
the selenium cell we have an action which only 
subsists while the illumination is proceeding, and 
which ceases when darkness supervenes. We have, 
in fact, a performance which, more than the photo- 
graphic camera, recalls the action of the human eye, 
which sees light only so long as it is there. 

What happens when darkness comes ? The answer 
is not far to seek, though it was sought in vain for 
thirty years after the discovery of the light-sensitive- 
ness of selenium. 

The electrons roaming about among the selenium 

atoms come across those among them which have 

been " ionised *' and have thus lost electrons. That 

loss implies a " positive charge " of the rest of the 



atom, and nothing is so effective in attracting an 
electron into an atomic system as the possession of 
a positive charge an unmated proton, so to speak. 
So the wandering electron promptly " goes home " 
and the electric field is deprived of one more slave 
to do its bidding. 

It is obvious that if there are many free electrons 
there will be many positively charged atoms, and 
the recombination of the ions will proceed more 
rapidly than if there are few. 

A detailed study of the rate at which the ions 
recombine throws a flood of light on the process of 
ionisation by light. Such a detailed study was 
undertaken by the Author in 1913. 1 

It showed that the diminution of the number of 
ions due to light in the selenium was always propor- 
tional to the square of the number of ions there. 
This is just what we might expect. For if we were 
to double the number of ions of one kind (say elec- 
trons) we should double the chances of recombination 
in a given time. But if we double both kinds, the 
chances will be again doubled, so that on the whole 
they will be quadrupled. 

Now we can see the reason why the conductivity 
of selenium does not at once return to its original 
value when the light is cut off. The free electrons 
produced by the light are at first very numerous, 
so that there are many chances of " mating " between 

1 " On the Efficiency of Selenium as a Detector of Light," Proceedings 
of the Royal Society, A., vol. Ixxxix, p. 75, 1913. 


electrons and protons, but as the reunited couples 
become more numerous, the unmated ions take longer 
to find their destined companions, so that complete 
reunion may require quite a long time. 

Now let us consider what happens when we turn 
on the light. The waves of light fall on the sensitive 
surface and penetrate into it not far, because 
crystalline selenium is an extraordinarily opaque 
substance. They churn up the atoms of the substance 
and shake out any loose electrons which may be on 
the verge of separation from their atoms. The 
number of electrons split off is proportional to the 
intensity of the light. This rule is again almost self- 
evident. For the " ionisation " of a single atom 
requires a definite amount of work, and the more 
energy enters the selenium, the more of that kind of 
work is done. It is the same in photography. 

But now comes the important difference. The 
recombination of ions sets in with the same activity 
whether the selenium is illuminated or not. The 
rate of recombination is simply a matter of how many 
ions are present. Ionisation and recombination 
proceed simultaneously. But since recombination is 
proportional to the square of the number of ions 
present, it increases rapidly as ionisation proceeds. 
There soon will be a limit at which the number of 
ions formed by the light equals the number of ions 
recombined in the same time. The selenium will 
then have attained the maximum of conductivity 
possible for that particular intensity of illumination. 


The energy of the light will then be proportional to 
the square of the number of ions formed. In other 
words, the number of new ions will be proportional 
to the square root of the luminous energy incident 
upon the selenium. In other words, the current 
due to the light will be as the square root of the illumina- 
tion. This important law was actually found to 
hold good by a number of investigators, including 
Rosse, Adams, Berndt, Minchin, and the Author. 

Having once obtained our law of light-action, we 
can follow it through every possible combination of 
circumstances. And first we must ascertain its 

There are several conditions which must be fulfilled 
before the law can operate. There must be a con- 
siderable number of electrons ready to be liberated. 
If the light is concentrated on a small area, that 
number may soon be exhausted and the formation 
of new ions may be brought to a standstill. Many 
authors have found our law to fail for intense illumina- 
tions, and have therefore proposed the cube root 
instead of the square root as a guide for the resultant 
conductivity. But for still greater intensities we 
should again have to change the index, so that it 
is better just to make the proviso that the illumination 
must be moderate. 

Is there a lower limit ? In my own experiments 
I tried illuminations so faint as to be equivalent to 
starlight from a single star, and still found the law 
to hold good. But if the new " quantum theory " 


is correct, no ionisation can take place below a certain 
amount of available energy. That amount of energy 
is excessively small/ but the eye is so sensitive that 
it can appreciate amounts of light down to the 
equivalent of some four hundred quanta falling upon 
the pupil per second, that being the amount of light 
received from the faintest stars. 

On the whole, we may say that there is no inferior 
limit to the sensitiveness of selenium so long as there 
is plenty of time to observe the action. It is only 
when the time is short that a limit is set to what we 
may discover. 

When the light is very feeble, the number of ions 
produced in a given time is very small, and the rate 
of recombination is very slow. For the feeblest 
illuminations it is, in fact, negligible, and ionisation 
proceeds steadily with practically no recombination. 
The number of free electrons mounts up at a uniform 
rate, and the pointer of our galvanometer will travel 
steadily across the scale. 

But the rate of travel may be very slow, and 
disturbing causes may become so important in com- 
parison that the experiment may be rendered useless. 
Selenium is very sensitive, for instance, to changes of 
temperature, and these may so distort the results 
that no conclusions can be derived from them. Such 
disturbances set a limit to the length of time for which, 
we can afford to wait for a result. 

We must next consider short intervals of time. 

1 Its amount is 5-2 X 10"* 11 erg. 


If the light is very feeble, a short exposure to it is 
of no use, as the ionisation will not have time to 
become perceptible. But if there is plenty of light, 
even a short exposure may give a clear and useful 
result. For however short may be the exposure, the 
amount of ionisation will be proportional to the 
intensity of the light, since recombination will not 
have time to set in and affect the result. If the 
exposure occurs in short flashes, the variation of 
conductivity between the flashes will be proportional 
to the intensity of illumination. This is another 
simple law which is of value if we wish to compare 
various amounts of light. 

It is obvious from the above considerations that 
a clear distinction must be drawn between the effect 
of instantaneous illumination and the effect of pro- 
longed illumination. The discrepancies between the 
results of former observers are largely due to a lack 
of this distinction. We may put the difference as 
follows : 

(1) The effect of prolonged illumination is propor- 
tional to its square root. 

(2) The effect of short illumination is proportional 
to the intensity of illumination and to the time 

Now let us see how these rules affect the use of 
selenium for discovering and detecting light of 
various kinds. 

Let us take a graphite selenium tablet which, with 
20 volts, has a resistance in the dark of 20,000 ohms. 


which, falls to 10,000 ohms on illuminating it with 
a candle placed at a distance of one metre. That 
amount of illumination is known as one "metre- 
candle/* or one " lux/' The current in the dark will 
be one milliampere, and in the light its final value 
will be two milliamperes. That final value will be 
attained in about five seconds. 

In order to deal with smaller amounts of illumina- 
tion, let us use the words " millilux " for one-thou- 
sandth of a lux, and " microlux " for one-millionth of 
a lux. The words milliampere and micro-ampere, 
similarly, are in general use for one-thousandth and 
one-millionth of an ampere respectively. 

If we place the candle at a distance of a thousand 
metres on a dark night it will just be clearly visible. 
The illumination produced by it will then be one 
microlux, since it varies inversely as the square of 
the distance. The instantaneous effect of the reduced 
illumination will be one-millionth of the previous 
value, but the final effect will be one-thousandth, 
that figure being the square root of one-millionth. 
We shall therefore get a micro-ampere on our gal- 
vanometer instead of a milliampere. That is quite 
a large current compared with the smallest currents 
which we can now measure. It will, however, take 
over an hour before the full effect is obtained. That 
would be inconvenient, so it is better in actual 
practice to limit the exposure to a short time, say, 
one second, in each case. That exposure will, in 
cases of faint light, rank as an " instantaneous '* 


exposure. We shall then get the following currents 
with the candle at various distances : 

1 metre milliamp&re. 

1,000 metres .... J microampere. 
400,000 , ..... ^ 

Now this last distance is the distance between 
London and Edinburgh. The current obtained, 
though very small, is easily measurable with delicate 
instruments, so that we should discover the presence 
of a lighted candle at a distance far beyond the range 
of human vision. If we make the distance a thousand 
times greater yet we attain the distance of the Moon, 
and the current obtained from' a candle at that dis- 
tance sinks to a millionth of a micro-ampere. Even 
that minute current is by no means beyond our range, 
for currents of that amount have often been measured 
with an Einthoven String Galvanometer provided 
with a silvered quartz fibre. Indeed, there is a way 
of measuring currents ten or even a hundred times 
smaller yet, by means of a delicate electrometer. 
But let us rest content with our result, which means 
that if anyone were to strike a match on the Moon, 
we could discover the fact on Earth by means of 
selenium, even without a telescope. And that feat 
could be accomplished in one second ! 

Matters are none the less remarkable if we do use 
a telescope. For the selenium cell, which considerably 
surpasses the unaided eye as a detector of light, would 
benefit by the telescope to the same extent as the 


eye. Tlie great telescopes of America will never 
be utilised to their fullest extent until they are used 
with selenium cells in their eye-pieces. 

There is another direction in which selenium far 
surpasses the eye. It is a well-known fact in photo- 
metry that the eye cannot distinguish a difference 
of "brightness much under 1 per cent. Suppose that 
two rooms are divided by a large door or partition of 
ground glass and that one of them is illuminated by 
a cluster of lamps, a hundred in number. There 
will be a uniform bright glow on the ground glass a& 
seen from the other room. If now one of the hundred 
lamps is extinguished, the observer may, with close 
attention and a well-trained eye, just discover the 
fact of the 1 per cent, extinction. With selenium 
this extinction could be revealed by a considerable 
movement of the pointer of a galvanometer. The 
Author tested this by the following experiment. 
A ground glass 2x2 inches was illuminated from 
above. Below it was placed a selenium cell con- 
nected with a Broca galvanometer and a battery of 
20 volts. A black thread was then stretched across 
the glass, in contact with the ground surface. It 
cut ofi 0-6 per cent, of the area of illuminated glass, 
no matter over what particular part of glass it was 
stretched. The thread produced a deflection of 
twenty divisions in the galvanometer^ This showed 
that a thread twenty times finer could have been 
discovered, which would have been thirty-three times 


less than any change of illumination discoverable 
by means of the eye, though aided by the best photo- 
meter ever constructed. 

This fact opens up a new vista in human perception. 
It means that we can discover shades much more 
delicate than those seen by the eye. There may, 
for instance, be clouds in an apparently clear sky, 
clouds which the eye cannot see on account of its 
inability to distinguish very faint contrasts. Again, 
things become invisible by moonlight or starlight 
not because there is no light, but because our eye 
has, in the course of ages, been trained and evolved 
to see chiefly the contrasts presented to us by day- 
light. Owls, mice, and cats have not lost their 
power of seeing in the dark as we have. Their eyes 
remain sensitive to the delicate contrasts presented 
by a room lighted only by the diffused gloaming of 
the night, or by the faint glow of the cat's own retina. 
There is, however, no reason why we should not 
recover that power by means of selenium. No 
" nightglass " or other telescope will enable us to do 
so, for no optical instrument is capable of increasing 
the contrast of extended surfaces. It can grasp a 
greater amount of light from a distant point source 
and so render visible a star invisible to the naked 
eye, But it cannot help us to distinguish the 
windows of a building a mile away in starlight, nor 
to find an enemy crawling towards us in the dark. 
It is quite conceivable that an instrument may be 
devised on the basis of the properties of selenium, 


which will, in effect, turn the night into day so far 
as visibility is concerned. 

The scientific importance of an enhanced perception 
of contrast can hardly be exaggerated. There are 
many investigations of liquids and solutions where 
an accurate estimate of transparency is essential. 
The first trace of a certain coloration or turbidity 
may be most important, and the eye is sadly deficient 
in the perception of such faint changes of luminosity. 
Hitherto, the only practical way of increasing the 
contrast of extended surfaces has bgen by means of 
photography. A faint contrast can be exaggerated 
by suitable methods of development. This is often a 
fault in portraits or landscapes, which turn out 
" harder " than they should, owing to an exaggerated 
contrast appearing on development. Purely optical 
instruments, such as telescopes and microscopes, 
are quite unable to increase the contrast of surfaces. 
All they can do is to spread the image of an object 
over a larger portion of the retina and increase its 
general brightness. The use of selenium will mark 
a new departure in the range of . optical instru- 

The actual mechanism of the ionising action of 
light is still somewhat obscure. But if some electrons 
are revolving in orbits round the atomic nucleus, 
under the influence of the attraction of its positive 
charge, any alteration of the electric field may convert 
that orbit from a circle or an ellipse into a parabola 


or hyperbola, and so lead to the expulsion of the 
electron from the atom. 

Such an expulsion of electrons actually takes place 
in the filaments of the thermionic valves used in 
wireless telegraphy. In this case the disturbance of 
the orbits is produced by the violent collisions 
between the atoms due to heat. Polished zinc will 
expel electrons under the action of ultra-violet light 
alone. Radioactive substances, such as radium and 
thorium, expel electrons spontaneously. X-rays are 
also effective in ionising selenium, but as they are 
much more penetrating than light-rays, a thicker 
layer can be used, and then the ionisation takes 
place through the whole substance. A thick plate 
of selenium can be used in order to determine a 
" dose " of X-rays, by observing the change of 
resistance in a slab of selenium. 

When we study the influence of colour on the 
effect of light, we find that red is by far the most 
effective in lowering the resistance of selenium. 
This does not necessarily mean that selenium is 
more sensitive to red than to the other colours. For 
in nearly all spectra which we command, there is 
more energy in the red than in the other colours. 
The maximum of energy shifts from the red end of 
the spectrum towards the violet end as the source 
of light gets hotter. The maximum effect on 
selenium shifts in the same direction. If we cut off 
the infra-red radiations, we cut off 26 per cent, of 


the effect, if we use a Nernst lamp as a source of 
radiation. If we cut off tlie ultra-violet rays as well, 
the effect is reduced another If per cent. In that 
case, the effective rays are mostly those of visible 
light. In sunlight the share of the visible rays is 
over 80 per cent. This is because the sun is hotter 
than any terrestrial source of light, and the maximum 
energy, instead of being in the infra-red, lies within 
the visible spectrum. 

If selenium is sensitive to one colour rather than 
another it is particularly sensitive to blue light. 
Blue light is more effective in its action on selenium 
than red light possessing the same energy. But 
selenium is not markedly " selective/' It is content 
to take its energy from the spectrum wherever it can 
find it in greatest abundance. 

It is certain that the law of light-action is the 
same for any kind of light, though the amount of 
action differs from one colour to another. Selenium 
can therefore be used with light of any colour, though 
it is usually best to employ red light as being the 
most "energetic" in terrestrial sources of light. 
Selenium cells can be " tuned " to different colours 
by covering them with coloured glasses. We can 
thus construct an automatic colour analyser, the 
amount of such primary colour present being indicated 
by a separate galvanometer. 

The equation to the recovery curve of selenium after illumination is 

1 * m 

_ _ __ = m 


where N is the number of electrons set free by the light and N is 
their number at a time t. B is a constant. 

The equation to the curve showing the light action is 

dN/dt = C N* 
where C is proportional to the intensity of the incident light. This 

is equivalent to the equation 

N = V(C/B)ta,n7i 
from which the light action of selenium in any given circumstances 
can be deduced. 



THE year 1880 was memorable in the Mstory of 
selenium in several ways. It was the year of Graham 
Bell's Photophone, and it was also the year when 
Shelford Bidwell first made a beam of light ring 
a bell. These two events seemed to place selenium 
in the very front rank of scientific and practical 
interest, and few people would have thought that 
another thirty years would elapse before the next 
steps were taken. But that sort of thing often 
happens in scientific discoveries. Twenty years 
elapsed between the discovery of induced currents 
by Faraday and Henry and the first practical dynamo- 
electric machine. 

Sometimes, indeed, a progressive step is taken 
in the dark, and is never found again. Every 
scientific investigator will have experienced this. It 
is a great mistake to assume that when a discovery 
is made it is a permanent acquisition of the human 
race. Many things may conspire to deprive us 
altogether of the use of the discovery. In the Middle 
Ages, when it was dangerous to be known to pursue 
natural knowledge and other " black arts/' discoveries 



were usually hidden away in cryptograms or died 
with their discoverers. We live in happier times 
now, but there are certain essential conditions which 
must be fulfilled before a discovery can see the light 
of day. In the first place, it must be capable of 
repetition. If Berzelius had found selenium in the 
residue of iron pyrites once, and had failed to find 
it again, his discovery would have been lost for a long 
time. Secondly, the discoverer must be convinced 
of the novelty of his discovery. If he thinks his 
observation has been anticipated by somebody else, 
he will not say much about it, nor take much interest 
in it himself. Thirdly, he must publish his discovery. 
This sounds easy, but often it is quite the most 
difficult part of it. He might write a letter to The 
Times or to Nature, but these journals would not 
publish his letter unless they knew the discoverer by 
reputation and were convinced of his judgment and 
trustworthiness. Failing them, he might present a 
report to a learned society. He can only do this 
through some member, and even then his paper will 
be referred to experts, who will be influenced by their 
personal or general knowledge of the writer. He 
might, of course, print a pamphlet independently 
and circulate it, but the scientific world would there- 
upon condemn him unread, arguing that if it were 
a true discovery, some scientific journal or society 
would have announced it. 

Another element which often contributes to the 
neglect of discoveries is their possible commercial 


value. An electrical engineer, seeing Mr. Bidwell 
ring a bell by means of a beam of light, might argue 
like this : " This discovery is either of commercial 
value, or it is not. If it is not, I take no interest 
in it. If it is, he has probably patented it, and I 
must give it a wide berth." So he waits until, 
fourteen years afterwards, the patent has expired. 
And as it is difficult to manufacture anything profit- 
ably in open competition, nothing more is heard of 
the invention. 

It was Edison himself who used to say : " Market- 
ing is 95 per cent, of an invention/' meaning that 
for every day spent on the invention itself, nineteen 
days would have to be spent on the business of finding 
a market for it. 

The world is only slowly waking up to the fact 
that discoverers and inventors are the most living 
part of the human social organism. They are the 
grey brain-matter, the cambium layer, the formative 
part of the whole. When life is not experimentation, 
it is routine, and of these two things, the former is 
surely the more alive. The organisation of research 
in the modern universities, the Nobel prizes awarded 
for great scientific discoveries, the medals and prizes 
given by learned societies, these are all encouragements 
to pure research which bear rich fruit. The prizes 
sometimes given by journals for some definite achieve- 
ment, such as the Daily Mail prizes for feats of 
aviation, are also valuable incentives, and have the 
advantage of being independent of the granting of 


patents and the subsequent troubles of marketing. 
Tliis system might be extended, with great advantage 
to humanity. 

Inventions involving selenium partake more of the 
nature of " cambium " than almost any others. For 
selenium is peculiarly human. It shows fatigue and 
after effects, just like the human eye. It can, like 
the latter, accommodate itself to darkness, and 
shows a diminished sensitiveness in a glaring light. 
It has also certain vagaries and uncertainties which 
recall the difficulties of depending upon the human 
factor in any enterprise. But all these qualities 
should help to strengthen the alliance between man- 
kind and the Moon-element. The difficulties need 
only be carefully studied to be successfully overcome. 

Shelford BidwelTs feat of 1880 remained for a long 
time a mere curiosity, and his apparatus was relegated 
to the category of " scientific toys/' It was only 
in 1900 that Clausen and von Bronk produced a 
signalling apparatus which could be used to indicate 
the Hghting-up or the extinction of a lamp by the 
ringing of a bell. _ The idea was to indicate the con- 
tinued lighting of a signal light (lighthouse or railway 
signal) in some important position. It made it 
possible to keep an automatic watch on, say, a distant 
lighthouse, by focussing its light on the selenium cell. 

As a current passing through a selenium cell is 
not capable of ringing an ordinary electric bell, it has 
to be sent through a relay which automatically 
switches on the bell current. This relay is best made 

FIG. s. 

(Seep. 8y.) 

FIG. 5. 


FIG. 18. 

(Barrfr Stroad,Ltd:i 


on the principle of the moving-coil galvanometer, 
first devised by d'Axsonval. A coil of wire, pivoted 
on the finest hardened pivots, moves in the magnetic 
field of a permanent magnet. The current from the 
selenium is sent through the coil, and as the resistance 
of the selenium is usually about 100,000 ohms, the 
coil may have a resistance of several thousand ohms 
without any disadvantage. Relays of this kind were 
made during the Great War by S. G. Brown, by 
Weston, by Sullivan and other makers and brought 
to a high degree of excellence. 

An interesting apparatus for the automatic lighting 
of harbour buoys was invented and constructed by 
Julius Pintsch, Berlin, and tried in the mouth of the 
Elbe. The buoys were lighted by gas which was 
turned on automatically at nightfall and lighted by 
a small permanent flame. At dawn the relay worked 
the gas tap in the opposite direction and extinguished 
the buoy. (Fig, 5.) 

An American project for the utilisation of selenium 
was a contrivance for sorting coloured objects, such 
as cigars or umoasted coffee beans automatically 
by their colour. The objects were allowed to slide 
one by one down an inclined groove. At a certain 
point they were exposed to a strong light. If they 
were of a light colour, they would reflect a good deal 
of the light, whereas if they were of a dark colour, 
they would not. The reflected light was received 
on a selenium cell, which actuated a relay if it 
received sufficient light from the object. The relay 


moved a switch which directed the objects down a 
certain path, so that the lighter objects were all 
collected in a special compartment. By adjusting 
the relay to various shades the objects could be sorted 
and classified according to depth of colour. 

The Great War of 1914-18 gave a great incentive 
to inventive activity among all the belligerents. In 
Britain, the use of selenium found a pioneer in Mr. H. 
Grindell Matthews, who had already distinguished 
himself by using wireless telephony to communicate 
with an airman in flight. He built a motor boat, 
which he called Dawn, and on this he installed a 
relay apparatus for controlling its movement by 
means of a searchlight. When the Zeppelin menace 
became formidable, he somewhat rashly offered to 
construct and control an aerial torpedo boat to be 
steered automatically from the ground and to attack 
the enemy in mid-air. His various attempts and 
achievements formed one of the romances of the war, 
and may well be set down here for the first time. 

Finding some difficulty in the working of selenium 
cells, which he had to obtain from Holland by special' 
messenger, he requested the Author to take charge 
of the design and working of the selenium apparatus. 
The Dawn was afloat on the Penn Pond, in Eichmond 
Park ! The searchlight used was of the torpedo-boat 
type, and had a 24-inch Parsons mirror. The arc 
light was supplied from a dynamo mounted on a 
traction engine. A large shed was erected near the 
pond to contain supplies and quarters for the night- 

Dr.Earron the risht. 

FIG. 6. THE " 


watclrman, but the pond was not specially protected 
or railed off, so tliat any onlooker could have wit- 
nessed the experiments. But onlookers were very 
rare indeed, and as it was winter the time referred 
to was November and December 1915 the Park was 
almost deserted. 

The selenium cell which controlled the action of 
the boat it was known as the Pilot consisted of 
an octagonal cylinder composed of eight graphite- 
selenium tablets each measuring 3 X J in., made by 
the Author. These eight tablets were carefully 
selected from a large number for their uniformity of 
quality. This was very important, as the boat would, 
of course, turn about a vertical axis passing through 
the axis of the cylinder, and the action had to be 
uniform all round. Any light-action on the selenium 
upset the balance of a st Wheatstone bridge " consist- 
ing of two " branches " of selenium (the " Pilot " being 
one of these) and two branches of graphite spread on 
" biscuit/' This was done so that temperature 
changes should have no effect, as they would act 
equally on the illuminated and the uniUuininated 
selenium. The requirements were that the boat 
should be able to (1) start ; (2) stop ; (3) turn to 
starboard ; (4) turn to port ; and (5) fire a gun, all 
these things being controlled by the searchlight. 
This was done by a sort of revolving commutator 
which put in the necessary switches in turn, the 
commutator being made to revolve by successive 
flashes of light acting on the selenium. It was 


found quite feasible to pick out any one of the five 
actions by making the commutator run through its 
five variations and dwelling on the particular one 
wanted at the moment. In steering to port the 
Dawn lighted a red lamp, and in steering to starboard 
she lighted a green lamp. 

While anxious days were being spent on trial trips, 
Mr. Matthews was undergoing a gruelling cross- 
examination at the Admiralty Board of Inventions 
and Research in Cockspur Street, then meeting under 
the Chairmanship of Lord Fisher. The greatest 
physicists of the country were assembled, and they 
turned the young engineer inside out, figuratively 
speaking, probing his knowledge of selenium and 
bringing forward all sorts of objections for him to 
answer. It was decided to subject the selenium 
tablets to a searching examination in one of the 
University Laboratories. This was done in the 
Author's presence. The tablets were exposed suc- 
cessively to extreme cold and to steam, to various 
vapours, to mechanical shock, and to prolonged and 
intense illumination. They " came up smiling " 
after every test, and their action remained faultless. 
No other selenium cells would have stood it. 

Then a bargain was struck between Mr. Grindell 
Matthews and the Government. He was to have 
250,000 if he could bring down a Zeppelin by means 
of an aerial destroyer worked by the new control. 
A deposit of 25,000 was to be made towards this 
sum as soon as satisfactory tests had been made with 


the unmanned boat and some otter applications of 

For tlie day of the great test, tlte Author designed 
and constructed a selenium mine, consisting of a 
selenium relay with, a telescopic lens 4 inches in 
diameter, directed towards the searchlight station 
half a mile away. On directing the searchlight upon 
the mine it was instantly fired by the action of the 
light on the selenium. As the image of the search- 
light mirror was focussed upon a small diaphragm, 
the "mine could not be exploded by any other search- 
light, even if it stood close beside the first one. 

The test was arranged for December 4, but the 
pond froze over that night, and it had to be postponed 
to the 7th. 

When the great day arrived, there was a bright sun 
all day long, and we all felt very nervous, because 
the sun might afiect the selenium and do its own 
steering, although the " Pilot " had been carefully 
shaded by means of circular discs of blackened brass 
spread over it horizontally. 

But the experts did not arrive till four o'clock, by 
which time the sun had sunk low enough behind the 
trees to be well out of the way. We saw the cars 
coming over the distant ridges. The Author did the 
final tuning of the selenium cells and relays on the 
boat and then went to look after the mine, half a 
mile away from the pond. 

The examining body arrived on the spot a great 
array of talent led by Lord Fisher. The Chancellor 


of the Exchequer and the First Lord of the Admiralty 
came, attended by a brilliant staff of the leaders of 
British naval and military opinion. Mr. Balfour 
stood by the searchlight, and commanded the evolu- 
tions to be performed by the Dawn. The little boat 
glided out from the small boatslip where she had been 
moored. She crossed the pond. A sweep of the 
searchlight, and she lighted her green lamp and 
turned to the left, performing a neat circle. Another 
touch of the luminous wand, and she made straight 
for the shore, but was stopped in time by a warning 
glance from the governing beam of light. She then 
started again and described figures of eight. For 
three-quarters of an hour the little boat careered 
twinHing about the pond, her red and green lights 
shining out alternately* It was the prettiest play 
of fairy lights ever seen. She finally fired her " gun " 
and returned to her moorings, with only her staunch 
selenium " Pilot " at the helm. 

The Author had " set " the mine, ready for the other 
experiment. An eye-witness from the shore of the 
pond described the effect as follows : " We saw the 
beam of the searchlight swing round to where we 
were told the mine was placed. It touched the spot 
and instantly we saw the flash and the column of 
smoke. The report reached our ears two or three 
seconds afterwards. It was most impressive." 

After the explosion, the Author was packing up 
the mine relay when he saw a messenger running 
towards him waving his arms. It was one of the 


mechanics, with a message that the company assem- 
bled wished to see the experiment repeated. The 
Author thereupon connected up the relay to another 
detonator, focussed on the distant searchlight and 
withdrew to shelter. The beam came round again, 
and another explosion shook the air. 

The test had been brilliantly successful, and the 
next day Mr. Grindell Matthews got his " deposit " 
of 25,000. He eventually worked the boat at sea 
at a distance of 3,000 yards in diffused daylight, 
and up to five miles at night. 

But the rest of the money was never paid, for 
within a few months other means of fighting Zeppelins 
had been discovered, and were found sufficient to 
remove that menace from our shores. 

Investigations concerning the possible use of 
selenium were continued for some time by the 
Admiralty, largely in a Selenium Laboratory placed 
under the Authors direction. One of the results 
of these investigations was Professor A. 0. Rankine's 
grid photophone, of which we shall hear more anon. 
Another application was a method of dropping bombs 
from small unmanned balloons by means of a search- 
light worked by either a friend or an enemy (prefer- 
ably the latter). Some very successful tests of this 
method were made at the Roehampton Aerodrome. 

Meanwhile, the enemy had not been idle. Recog- 
nising that the action of selenium is liable to numerous 
irregularities, Dr. Chr. Ries, a German authority on 
selenium, had constructed a differential selenium 


relay, wMcli only worked on exposing it to slowly 
intermittent light, and was then actuated by the 
difference of the conductivity in light and in the dark 
respectively obviously a much more reliable action 
than any action depending upon the actual value 
of the conductivity. 

But on the whole, there is no evidence that 
selenium was put to any actual military use during 
the war, not, at all events, with relays. The chief 
reason was that military men are shy of " delicate sy 
mechanisms. A military adviser of the Munitions 
Inventions Department put the matter very tersely : 
fe Micro-amperes," he said, " and military operations 
simply don't go together/ 5 Much can be said both 
for and against that dictum. After all, explosives 
are dangerous things to carry about, yet they are 
handled every day by soldiers with impunity, though 
a spark or a scratch might blow them sky-high. 
The safety lies in the adjustments and safeguards 
prescribed by the inherent dangers themselves. 
None of the mechanisms used in warfare are one- 
thousandth as complicated as the human mechanism 
itself, and yet the latter is what ultimately decides 
the fate of a battle and the history of a nation. It 
is often the most complex things which are also the 



EVER since tlie invention of the electric telegraph 
tlie transmission of pictures has been an inventors' 
dream. The dream has gradually very gradually 
come true. The slow progress made is largely due 
to a wrong conception of the difficulties of the prob- 
lem. An artist will make a " lightning sketch " in 
a few minutes. A line here and there, a wash of 
colour in the right place, and the " picture " is com- 
plete. What inventors do not realise is that the 
smallest picture consists of several thousand dots. 
Even a " line " is really a row of dots, almost invisibly 
fine. The line on the paper may be continuous, but 
the image of the line on the retina is invariably dis- 
continuous, and consists of a row of dots adjoining 
each other. A " wash " therefore means the creation 
of an immense array of dots thousands of them 
and before each dot can be put into its proper place, 
the telegraphic transmission becomes a very formid- 
able matter indeed. 

The first attempts were made to transmit hand- 
writing and line drawings generally. A beginning 
was made in England by F. C. Bakewell in 1850. 



He wrote with a grumpy ink on a tinfoil-covered 
revolving cylinder. At the receiving end a similar 
cylinder was made to revolve at the same rate, and 
every time a gum line passed a certain contact a 
chemical action was produced on sensitive paper 
at the receiving end. 

In 1856, Caselli, an Italian, exhibited in England 
an apparatus called a " pantelegraph/' which had 
quite successfully transmitted from Paris to Marseilles 
not only writing, "but plans, drawings, and pictures ; 
but it was found that it suffered from the defects of 
BakewelFs apparatus, and was complicated and costly. 

Twenty years after that the Post Office authorities 
in London conducted a series of experiments with 
D'Arlincourt's apparatus. The principles of this 
were similar to those employed by Bakewell, but a 
distinguishing feature was the introduction of an 
ingenious synchronous movement which rendered 
the revolving of the cylinders at the two stations 
absolutely uniform. With this instrument repro- 
duction in blue, brown, red, and black, according 
to the nature of the chemical composition employed, 
was perfect ; but it still had one drawback in common 
with its predecessors that of slowness of operation. 
It was, however, used extensively by the French 
authorities for military purposes. 

Shortly after this Cowper introduced his famous 
"writing telegraph." This introduced an entirely 
new principle that of actuating a pen at the receiving 
station by merely writing with a pencil at the trans- 


mitting end of the circuit. The system, however, 
necessitated the employment of two lines, through 
each of which passed currents smoothly increasing 
and decreasing in intensity. The pencil at the trans- 
mitting station was fixed to two arms, placed at 
right-angles. These arms directly actuated variable 
resistances, and thus varied the currents in the lines 
in accordance with the position of the pencil. Ee- 
ception was by means of two needles magnetically 
pulling in opposition to light springs upon the record- 
ing pencil. 

Although the " telewriter " has become a regular 
feature of certain classes of business, it must be 
admitted that any method depending upon the syn- 
chronic motion of two cylinders is bound to be 
complicated and costly. 


There is, however, nothing in the way of " coding " 
a picture, i.e. dividing it into a large number of dote 
and indicating the average shading of each dot or 
patch by a letter, which is telegraphed in the usual 
way. Such a transmission of a coded picture was 
made by the Author on May 24, 1923. It was, 
however, not transmitted by telegraph wire, but by 
wireless radiotelephony from the London Station of 
the British Broadcasting Co. It was the first attempt 
ever made to broadcast a picture, and as the time 
of transmission was limited to twenty minutes, the 


result was necessarily crude. It being Empire Day, 
it was decided to " broadcast " a portrait of King 
George V. 

The Author prepared the cipher message by 
coding a portrait of His Majesty. This was done by 
putting the original picture in an enlarging camera 
and projecting a magnified image upon a ground-glass 
screen marked out into 600 small squares, arranged 
in 30 lines of 20 squares. A code letter indicating 
the average brightness was then assigned to each 
square, and these code letters were then written out 
in 30 lines of 20 letters each. 

The code letters and symbols were carefully chosen 
to facilitate telephonic transmission and subsequent 
reproduction. There were six of them, announced 
as follows : Stop, X, I, J, G, M. It was explained 
that " stop " was an ordinary full stop, or (if a type- 
writer was used) a hyphen. A blank space was 
indicated by the vowel 0. 

It will be noticed that these letters have very 
different vowel sounds, so that they can be dis- 
tinguished even if the consonants are not clearly 

On Empire Day the code was explained and dic- 
tated by the Author. The dictation of the 600 
letters took twenty minutes, although previous 
experiments had shown that an adult could easily 
take it down in eight minutes or less. Each line 
of 20 letters was divided into four groups of 5 letters 
each. This was to avoid confusion and facilitate 



subsequent reproduction. The complete cipher 
message is given below : 



. - . -g 
- - gmg 
. gmmi 
. g . oo 

gg 00 

mgo o o 
mg . o o . 
m i j m . 
mg . m . 
gggg - 
3 i g g - 
g m m x m 
j m g i g 
j Jig 
. mmx 
mmg , 
m m m m . 
m m m m . 
mgg . x 
mxx . g 
mj jig 
mj j xi 
mi i i 

n j i i 


- iggg 


o o o o o 
o o o o o 

. O 


gjx . . 

gixx . 

. . O . 

o . . . . 
xo . . x 
mgi , . 
mgg . i 
mgm i . 
x . . xx 
x i i j j 
m j i i i 
mj . ij 


gmmm j 
mmg j i 
i m j . g 

g. . . . 

gg - - - 
j J g - - 
. mm . . 
o m j . . 
i J J - - 
igjx - 

J? 1 : - 

i i j i 

g j . . 

jg. . . 

iig. . 
xxo . 
x .... 

X i J . . 

3 j i g j 
j gmmm 
ggg -x 
m . . . . 
x .... 





. . . mm 

. g mm 
gmin mm 

mj imm 
j i g m m 
i j m m m 

The picture was received and built up from the 
code on squared paper by some 250 " listeners " in 
various parts of England. 

The limitation of a picture to 600 dots was, of 
course, a severe handicap. But no picture need 
have more than 10,000 dots, since the yellow spot of 
the retina the portion of the eye which we all use 
for distinct vision has only 10,000 separate nerve- 




endings, and we could not " clearly " see more titan 

that number of separate 

Although tMs was the 
first attempt to broadcast 
a picture, the transmis- 
sion of coded pictures by 
ordinary or wireless tele- 
graphy had been carried 
out before. Mr. Sanger- 
Shepherd had transmitted 
coded pictures across the 
Atlantic, the code being 
automatically produced by 
a perforating machine 
worked by a selenium cell, 

the perforations in the same small area being from 
one to six in number, according to the brightness of 
the patch coded, and the perforations being optically 
recombined into a patch of the proper grade. 


But the transmission of pictures by means of 
selenium was usually accomplished with the help 
of two synchronously revolving cylinders. This was 
done most successfully by Korn, who on November 
8, 1907, transmitted a portrait of King Edward VII 
from Paris to London in twelve minutes. 

The method was to draw the portrait in successive 
vertical lines, seventy-five to the inch. These lines 


were graded by passing the original picture in front 
of a selenium cell which controlled a shutter apparatus 
at the receiving end, thus reproducing the portrait 

Some such method was also used by Mr. Thorne 
Baker in England. More recently, selenium has 
been discarded in favour of bichromated gelatine , 
which gives an image in relief capable of actuating 
contacts on the revolving cylinder of the transmitting 

Another contrivance which has been tried in this 
connection is the " photo-electric cell/' a vacuum 
tube provided with two electrodes, one of which is 
a colloidal- film of potassium or rubidium. When 
this film is charged negatively, it emits a stream of 
electrons under the influence of light, which instantly 
ceases on the restoration of darkness. This instan- 
taneous action is a very valuable property, and would 
be still more valuable if the currents so obtained 
were not almost immeasurably small. 

M. Belin, a French electrician, is said to have 
transmitted the shadow of a small square practically 
instantaneously by wireless telegraphy on the above 
principle, but it must not be forgotten that Erfist 
Ruhmer had attained a similar result by means of 
selenium before his death in 1913. 

Such rapid transmission of pictures bring us within 
measurable distance of the solution of what is known 
as the problem of " television," or electric vision at a 



Let us state tlie problem. A scene or object to 
be transmitted may be regarded as a changing 
picture. In order to reproduce it at tlie receiving 
end, the picture must be then presented as rapidly 
as a kinema picture, which, changes some twenty 
times per second. If we can, therefore, transmit a 
picture in a twentieth of a second, we have solved the 
problem of " television." 

We can at present transmit a picture in about five 
minutes. The present rate is, therefore, about six 
thousand times too slow. Can we accelerate it six 
thousand times ? 

Let us put it in another way. A picture of, say, a 
human face cannot be divided up into less than 
some four hundred uniform patches without becoming 
difficult to recognise. We must therefore transmit 
fora hundred signals twenty times per second, or 
eight thousand signals per second, and these signals 
must indicate the luminosity of each patch in at 
least six different grades. This, however, can be 
done by means of permutations of the Morse dot and 
dash, so that we have to transmit sixteen thousand 
signals per second. Can this be done ? 

The answer is at present in the negative. There 
is no way of producing an action of light in a sixteen- 
thousandth of a second which could be effectively 
telegraphed, either by wire or by wireless. 

Quite recently, however, the Author has found 


that "by using intermittent liglit of many different 
musical frequencies, each, frequency corresponding 
to a separate portion of tlie original picture, it is 
possible to transmit these portions simultaneously 
by means of the same selenium cell. The musical 
frequencies are impressed upon the" carrier wave of 
a wireless transmitter, and are reproduced in a loud- 
speaMng telephone at the receiving station. 

The picture is then " heard yy as a medley of sounds, 
each sound representing a portion of the original 
picture or object to be transmitted. 

The sounds are then analysed by a set of resonators, 
each of which picks out its own note and projects a 
luminous patch on a screen in its proper place. The 
original picture is thus reconstituted in a small frac- 
tion of a second. 

As several hundred resonators can be employed, 
the problems of telephotography and television are 
thus brought nearer to their final solution to the same 



WHAT changes are likely to take place in our optical 
instruments within the next hundred years ? The 
first telescope was made by Hans Lippershey in 1609. 
He was a Dutch watchmaker, who had a collection 
of all sorts of spectacle glasses. An apprentice of 
his happened to put two of them together in such 
a manner that they magnified a distant church 
tower. The master saw the possibilities of the 
situation and was quick to turn them to account. 

G-alileo heard of this and made up his own telescope 
in accordance with what meagre details he could 
obtain. The result was the Galilean telescope the 
present-day opera glass and the discovery of 
unimagined marvels in the ky. 

The microscope had a steady evolution from the 
magnifying glass, already known to the Romans 
and the Chinese. It is now capable of magnifying 
some five thousand times, and a modification of it, 
called the ultra-microscope, is capable of showing 
the presence of much smaller objects by their diffrac- 
tion images. 

The functions of both instruments are very simple. 



They serve tlie purpose of spreading tlie image over 
a larger portion of the retina and of increasing its 
general luminosity. They cannot increase the con- 
trast of luminous surfaces, and this is a severe limita- 
tion of their utility. We have already referred to 
the possibility of selenium stepping in here to remove 
that limitation, Some years ago/ the Author put 
this possibility as follows : 

" We must next consider the capacity of selenium 
for detecting small variations in brightness. This 
is a field hitherto entirely neglected, which yet^ opens 
up immense possibilities. We will assume, as before, 
that an illumination of 1,000 lux on a selenium surface 
of 100 cm. gives, with 10 volts, an extra current of 
1 ampere. What is the smallest variation of illumina- 
tion we can discover ? The utmost limit of delicacy 
with which the eye can discover differences in 
luminous intensity, when armed with the best photo- 
metric means, is one half or one third per cent. This 
would vary the current by one quarter or one sixth 
per cent., or by, say, 2 milliamperes. This is enor- 
mously in excess of the smallest current measurable. 
There is no reason, in fact, why variations as low as 
1/100 or even 1/1,000 per cent, should not be dis- 
coverable with certainty. In experiments tried up 
to the present it was found comparatively easy to 
discover variations of 0-03 per cent. 

" The importance of these facts in countless physical 
and chemical processes is bbvious to any physicist 
or chemist. But let us carry the appeal before a 
more numerous class of readers by the following 
consideration. A landscape under moonlight or 
starlight is not as clearly defined to our eyes as a 

1 Stienfca, September 1916, 


landscape under daylight because we fail to perceive 
the contrasts. If there were any physical means of 
enhancing these contrasts the difference between 
a landscape by day and the same by night might be 
considerably reduced or even annulled. Now it is 
a well-known law of optics that no optical system or 
instrument can alter the intrinsic brightness of an 
extended surface, though it may make a point source 
appear more luminous. It is therefore impossible 
to obtain a telescope which will increase contrasts 
of contiguous surfaces. If, on the other hand, we 
could use selenium as an intermediate receiver, and 
retranslate its indications into light, we might make 
a nocturnal landscape appear as clear as day an 
obvious advantage for military and other purposes/' 

Every user of a large telescope will have noticed 
that as the magnification of an object, such as the 
Moon, is increased, the contrasts become more and 
more vague, until the Moon's surface appears but 
a patchwork of cloudy blurs. That is because with 
every new magnification the gradient of contrast 
becomes less steep. If we could utilise the contrast- 
discovering powers of selenium we might, for instance, 
discover details on the floor of that mysterious large 
crater known as Plato which have hitherto defied 

But quite apart from this possibility, there is much 
reason to believe that our optical resources, which 
for centuries have developed along the same grooves, 
are capable of entirely new departures. 

Take the case of the projector or searchlight. The 
principle of the searchlight is to place a small but 


intensely luminous source at the focus of a parabolic 
mirror, so that a beam of parallel light piay issue 
from the mirror. The diameter of this beam to 
begin with is the diameter of the mirror itself. It 
would remain of the same diameter if the source 
were a geometrical point. But no visible source of 
light is small enough to be considered as a geometrical 
point, and so the beams diverge. That divergence 
is not obvious. It is a curious circumstance that 
during the war many trained electricians and physi- 
cists were under the impression that the diameter 
of a searchlight beam is the same, say, at half a mile 
as it is where it issues from the searchlight mirror. 
It certainly looks as if it were quite parallel, as seen 
from the mirror. But if it were, it would appear to 
converge in the distance, like railway lines. The 
very fact that it appears not to converge should have 
shown them that in reality it diverged and spread. 

Now consider the effect on a small object, say the 
dial of a clock a mile away. If we reduce the 
diameter of the mirror and reduce its focal length in 
the same proportion, we can also reduce the size of 
the luminous source. As a result, we shall have the 
same result on the distant clock face as before. And 
we shall have saved ourselves the trouble of construct- 
ing a large and expensive mirror. Not only that, 
but the source of light will be cheapened in proportion. 

Now a hundred small mirrors or lenses are much 
cheaper than one mirror or lens of the same aggregate 
surface. We should, therefore, gain considerably by 


using a large number of small optical systems instead 
of one large one. 

That is what the insects do. Their composite eyes 
are one of Nature's experiments which has stood 
the test of time. We ought to construct receiving 
instruments on the same principle. It is true that 
we cannot directly apply such composite instruments 
to our eyes, but we can recompose a picture from the 
elements yielded by the several lenses and then con- 
template it. 

We can make our elementary searchlight beam as 
narrow as we choose by suitably increasing the focal 
length of the lens or mirror. We can do the same 
with a composite telescope, so that there is nothing 
to hinder us in making whatever fine-grained analysis 
we please of a distant object. 

The impending solution of the problem of television 
will bring us face to face with these new aspects of 
optical data, and will open up enormous vistas of 
scientific and practical advancement. 



WE liave already seen in Chapter III (p. 54) that 
the instantaneous effect of the impact of light on 
a selenium cell is what physicists call a 6e linear " 
one, meaning that it increases directly as the duration 
of the illumination. This relation enables us to 
calculate for any given intermittent illumination the 
amount by which the current in the selenium circuit 
will vary. 

Let us take an example. A light of a hundred 
candle-power, shining upon a selenium cell placed 
at a distance of one metre, produces a current of 
one-tenth of a milliampdre in one-tenth of a second. 
Then in one-hundredth of a second it will produce 
a current of one-hundredth of a milliampere, or ten 
" micro-amperes." Similarly, in a thousandth of a 
second it will produce a current of one micro-ampere. 
Now what happens if we throw such a beam upon a 
selenium cell every other thousandth of a second ? 
Obviously, there will be five hundred flashes per 
second, each lasting for that short interval of time, 
and each of them will temporarily give rise to a 
current of a "millionth of an amp&re in the circuit, 



Let us send that current through a sensitive telephone 
receiver. The telephone will instantly respond and 
will sound a note one octave above the middle C of 
the piano. We shall have "converted light into 
sound' 5 through the medium of an electric 

That this " conversion " is symbolical rather than 
actual is evident when we consider the enormous 
disproportion of sound-waves and light-waves. 
Sound-waves are measured in feet, and are repre- 
sented by the lengths of organ pipes. Light-waves 
are from forty thousand to seventy thousand to the 
inch, according to their colour. In duration they 
are even farther apart. If we could slow down an 
average light-wave until it took one second to pass 
us, and could slow down an average sound-wave in 
the same ratio, it would take no less than two hundred 
million years to pass by ! 

In spite of this enormous disproportion, it is a 
remarkable fact, recently established by very pains- 
taking researches, that the smallest amount of energy 
perceptible as sound by the ear is just about the 
same in amount as the smallest amount of energy 
perceptible by the eye as light. If the new " quantum 
theory " applies to both forms of energy, it means 
that both our senses have accommodated themselves 
to the minimum quantity of energy in existence 
provided it comes to us in a constant succession of 
pulses frequent enough to produce an impression of 


An apparatus for " converting light into sound " Is 
shown in the illustration (Fig. 8, p. 67). 

The round case contains a glass plate on which 
sections of blank paper are mounted, leaving a series 
of radial slits. These pass the aperture a when the 
handle is turned and the adjustable slit s transmits 
light when each radial slit passes. The springs f are 
intended to clamp a selenium cell in front of the slit s. 
If the cell is put in circuit with a battery and a tele- 
phone, a musical hum is heard which rises in pitch 
as the speed of rotation increases. It is best to place 
a bright lamp on the other side of the case. If an 
object is passed between the case and the lamp the 
sound ceases instantly. There is no lag or after-effect 

Since the fluctuations of current are greatest at 
the lowest speeds, we might naturally expect the 
lowest notes to have the loudest sound. But that is 
not the case. The reason is that the human ear is 
not particularly sensitive to sounds of a low pitch. 
If they do sound as loud as higher notes, it is because 
their energy is much greater. A male voice expends 
much more power than a female voice if both speak 
equally loudly. A baby's voice, though it may 
sound very loud, consumes feast energy of aU. This 
means that Nature has made our ears respond most 
readily to those cries which convey the greatest 
need of help. Would that such could be the general 
law ! 

We shall see in the next chapter how this " con- 


version" of light into sound has been utilised to 
relieve the disabilities of the blind. 

As the question of reversing the process and 
" converting sound into light " is likely to become 
a pressing one in the near future, we may here 
briefly consider one method of accomplishing this 

It was recently worked out by the Author, and 
consists of receiving the sound in a tube having a 
vertical portion closed with a thin rubber sheet 
stretched horizontally. 

Mercury is carefully poured on this sheet until 
it forms a drop about one-third of the diameter of 
the rubber sheet. .The surface of the mercury is 
observed by daylight or artificial light. As the sound 
of the music or speech is received, the mercury is 
observed to " crimp " itself into an ever-changing 
variety of patterns. The remarkable thing about 
these patterns is that they are produced instantane- 
ously, and remain unchanged so long as the sound 
remains unchanged. They are extraordinarily sensi- 
tive to variations of pitch, and therefore furnish a 
severe test for a singing voice. 

A better view of the patterns may be obtained by 
throwing the beam of a* torch lamp slantingly on to 
the mercury and receiving the reflected light on a 
screen of ground glass, taking care that no direct 
light falls on the latter. But the best way is shown 
in the diagram, Kg. 9. Light from an arc lantern 
or a gas-filled lamp is received by a lens so as to 


(See p. 15 5.) 

I'lG. 1.1.TOXO&KAM", XOTE B PLAT. 1'IG. 10 T050GSA3I. NOTE F. 



produce parallel rays. The beam is reflected verti- 
cally downwards on to the mercury, which reflects 
it upwards into another prism. The latter, in turn, 
reflects it into the 
original direction 
until it falls on to a 

The tube holding 
the mercury may be 
substituted for the 
visible horn of an 
old - fashioned 
gramophone, in 
which case the 
gramophone tune 

will be very graphically shown. Or the brass tube 
may be turned aside at the bottom in a horizontal 
direction and used for receiving the spoken voice. 
The photographs show some voice records produced 
in this way. It will be seen that the higher the 
pitch the smaller is the wave on the pattern. (See 
Figs. 10 and 11.) 

The waves remain stationary so long as the note is 
kept at the same pitch. They are produced by the 
rubber communicating its vibrations to the edge of 
the mercury drop. The waves travel to the centre 
of the drop and then out again, the incoming and 
outgoing waves combining to form the stationary wave 
patterns, much as we can see them do at a vertical sea 
wall when the waves are coming straight towards it. 



THE present chapter will give an account of how the 
reading problem of the blind was completely solved 
by means of selenium so far as printed books and 
newspapers, as well as type-written documents, are 

It will tell how the first attempts at a solution were 
made, what difficulties were encountered, and how 
the final solution of the problem was received by 
those entrusted with the welfare of the blind. 

In the year 1910 the Author was appointed Assist- 
ant-Lecturer in Physics in the University of Birming- 
ham. The salary attached to the appointment 
150 a year was not exactly a tempting one, but 
the duties were light and the real attraction lay in 
the magnificent equipment of the Physics Department 
of the University, which had just opened new buildings 
at Bournbrook. Professor Poynting, who held the 
Chair of Physics, was a man of world- wide repute, 
and he had taken care that the new Physics Depart- 
ment should be the last word in facilities for research. 
Moreover, he administered a special fund amounting 



to 150 a year to be spent on new apparatus, the gift 
of a well-wisher of the University. 

With the active encouragement of the Professor, 
as well as of the Principal of the University (Sir Oliver 
Lodge), the Author started a research on the pro- 
perties of selenium, feeling sure that that elusive 
element would amply repay a further prolonged study. 
He particularly investigated the manner in which 
selenium violates Ohm's law and the way in which 
the effect of light varies as the illumination is reduced 
to the lowest effective amounts. After reading 
papers embodying the results of this study before 
the Royal Society, he turned his attention to certain 
practical applications which had occurred to him. 
One of these was the utilisation of the action of light 
on selenium for the purpose of recording star transits. 
He succeeded in making Aldebaran, a first-magnitude 
star, ring a bell in its passage across the meridian, 
and also in making it work an electric chronograph. 
This was done by means of a 3-inch transit telescope 
(which had been used for timing the London coach 
in the days before railways were built) and a Kelvin 
mirror galvanometer. 

Having obtained these considerable mechanical 
effects from very small amounts of light, the Author 
proceeded to study the question of making the wonder- 
ful properties of selenium available for relieving the 
disabilities of the blind. 

The fact that light could be made to ring a bell 
showed conclusively that in one respect, at least, 


tile ear could be substituted for tlie eye. But that 
fact lad been known for some twenty-five years, 
during which the resources of science had increased 
almost immeasurably. It only remained to harness 
them "bo the work. 

The Bell telephone receiver, invented in 1876, is 
an instrument of almost unsurpassed power to detect 
minute currents of electricity. The only radical 
improvement achieved since Graham BelTs days was 
the invention of the reed telephone receiver by Sidney 
G. Brown in 1912. This improved receiver, which 
worked a conical diaphragm of the lightest aluminium 
sheet by means of a reed attracted by magnets, was 
found to be capable of detecting currents of less than 
a millionth of an ampere, provided they were regularly 
interrupted. The Author perceived the value of 
this new detector and proceeded to apply it to the 
detection of light falling upon selenium. 

Since selenium conducts electricity to some extent 
even in the dark, it was necessary to compensate the 
** dark " current by some arrangement of the circuit, 
such asthe system known as the " Wheatstone bridge/' 
which consists of four conductors arranged in a square, 
two opposite corners of which are joined to the poles 
of a battery, while the remainder are joined to the 
galvanometer or other detector in this case the 
telephone receiver. If now one of the four conductors 
is a selenium cell, while the others are resistances of 
the same value as the dark selenium, there will be 
no current through the detector while the selenium 


remains dark. But when it is illuminated, the 
balance of resistances will be upset and a current 
will flow through the detector. Since, however, a 
steady or slowly varying current produces no sound 
in a telephone, it is necessary to interrupt it. This 
is done by clockwork in practice a small clock in 
which the escapement is replaced by a vane in steady 
rotation, while one of the cog wheels is used to make 
contact with a spring. 
This was the construction of the first exploring 


Optophone. It worked very satisfactorily, but the 
Author soon found that it was much more useful to 
discover contrasts of adjoining objects and surfaces 
rather than trying to gauge the brightness of surfaces 
as they came within range. He therefore adopted 
a Wheatstone bridge containing two adjoining 
selenium cells, both of which were exposed to the 
light object to be explored. In the annexed diagram, 
Se Se are the two selenium cells, and C and C are two 
graphite resistances of about 10,000 ohms each, 


joined by a variable resistance of manganin 

The selenium tablets, resistances, battery and 
clockwork were built into a small case resembling a 
photographic camera, closed in front by an iris 
diaphragm. A telephone receiver was connected 
to the bos by flexible wire. The whole apparatus 
was self-contained and quite portable. (See Fig, 13.) 

The instrument was first shown in action at the 
Exhibition organised by the Optical Convention of 
the United Kingdom, held in the Science Museum at 
South Kensington. 

The reception given to the exhibit by the Press 
was unexpectedly cordial. The invention seemed to 
fire the popular imagination, and if a gust of ephemeral 
fame had been the boon sought by the Author he 
had reason to be amply satisfied. As it was, the 
interest created by the invention strengthened his 
hands in facing the determined opposition called 
forth by later developments. 

The PaU MaU Gazette of June 24, 1912, announced 
the first demonstration in the following whimsical 
paragraph : 

" To-morrow the Optical Convention is to let loose 
a new invention on the world. An ingenious Birming- 
ham scientist has turned the element of selenium to 
account by making light audible, and we are to be 
dazzled and deafened both at once. Sunlight makes 
a roaring sound, and lightning, presumably, antici- 
pates its concomitant thunder. All we require now 


' I' *>'<&:' '-^ > /V J * '*$'>'/"'''*'? , ' ''/ ''/''' ;', . 

' """' 

^yv%lV/ '" ;',, '- Vl 

?f"' ' ; p- '.' :;i; ; > ' ; 




is to increase the anticipative process, and then day- 
light will waken us every morning a couple of minutes 
before it arrives. What a point for the daylight- 
savers ! Let us hope, however, that nohody wiU 
interfere to make darkness audible as well, for that 
would ' make night hideous ' indeed/' 

A rather more sober announcement was made on 
the same day by the New York Sun : 

Special Cable Despatch to the " Sun " 

, June 24. Dr. Fournier d'Albe, a lec- 
turer on physics at Birmingham University, will 
demonstrate to-morrow at the optical convention at 
South Kensington an instrument caEed the opto- 
phone, which is designed to enable those who are 
totally blind to locate and estimate light by means 
of the ear. 

" The instrument is based on the property of 
selenium of changing its resistance when it is illumin- 
ated. This change is made to cause a current which, 
when interrupted by a special contrivance and 
transmitted through telephone receivers fitted to 
the head, gives an audible sound varying in loudness 
with the intensity of the light. 

" The blind are enabled to locate lamps in windows 
and other high lights and to trace the outlines of large, 
well-defined objects. The instrument makes the 
moonlight distinctly audible and sunlight a roaring 

The Daily News and Leader of the same date 
published an interview with the inventor, which 
contains a forecast of the type-reading optophone : 


" * It is the first stage in making the eye dispen- 
sable/ said Mr. Founder d'Albe. The initial difficulty 
of making the blind susceptible to light having been 
conquered, he is optimistic as to the results which 
further study and experiment may yield. 

" * The ultimate object, to provide a complete 
electrical substitute for the human eye, must be a 
matter of time/ he said, ' but by-and-by I hope to 
enable blind people to discover all sorts of objects 
in a room without exploring at all. To teach them 
to read print by sound may, of course, take years, 
but I am going to try/ " 

The demonstration was given on June 25. Some 
blind persons had been attracted to it by the Press 
announcements, and one of them volunteered to test 
the apparatus. The account of what took place was 
given in the Daily News as follows : 

" What happened yesterday was this : The blind 
man sat by a little table scattered with all manner 
of electrical contrivances, fixed the earpieces over 
his head, and took the black box in his hand. 

" * You are quite blind ? * asked Mr. Founder 

" ' Absolutely/ was the reply. 

" * Now, point the box in this direction, and tell 
me what you hear/ 

" Mr. B obeyed. He pointed the box to the 

window. * I hear a very rapid buzzing, like the 
whirring of a telegraph wire/ he said. ' Now the 
noise is growing louder and louder y the box was 
pointing straight to the sun * now it is very loud 
indeed ' 

"Mr. d'Albe silently passed his hand over the 
aperture. f And now ? * he queried. 


" * Complete silence ! 9 was the reply. 

" The light had been shut out, and there was no 
more whirring. 

" ' Good ! * remarked the inventor. * I have tuned 
the machine to whirr when the box is pointed to the 
light, and to be silent when it is moved away from 
the light. Is that audible to you ? * 

" f It is quite clear ? * said the blind man. * I can 
hear the light. . . / There was a tragic little note 
of sadness in his voice/" 

The Daily Chronicle gave particulars of another 
kind of experiment : 

" Another test applied to the same blind man was 
to equip hiTn with the apparatus and start him to 
walk round the room with instructions to find a 
window. This he did several times without a single 
failure. The Optophone, as Mr. Founder d'Albe 
explained, had been * silenced for darkness/ and the 
moment the blind man approached a window the 
ticking or rasping sound became audible to his 

" He was listening to the light, as previously he 
had been listening to the shadows of the men who 
had passed in front of the Optophone/' 

Finally, an experiment was made at the suggestion 
of Mr. Arthur R. Burrows (now Director of Pro- 
grammes of the British Broadcasting Co.). It was to 
see if the Optophone could be used to hear the light 
of a match. It so happens that selenium is particu- 
larly sensitive to low-temperature light like that of 
burning wood, so it is not surprising that the experi- 



ment was completely successful (see illustration, 
Frontispiece). ** 

Within a few weeks of tie demonstration the news 
of the invention had travelled all over the world. A 
vast amount of correspondence reached the Author, 
some letters, written in the quaintest English, coming 

from Upper Egypt and 
India. They wanted to 
know more about " the 
machine that makes the 
blinds to see " an ex- 
aggeration almost un- 
avoidable when papers 
copy and translate from 
one another. 

" You have had a 
magnificent Press," said 
a famous man of science 
to the Author. " Now 
if I had had a Press like 

that " he smiled 


But he was wrong. The people who mattered were 
the blind, and they can only be reached through the 
Institutions which care for their welfare. Sir Wash- 
ington Ranger, the famous blind solicitor, wrote to 
the Author to say that he saw no utility in the in- 
strument. " The blind problem is not to find lights 
or windows, but how to earn your living/' The 
Author is ashamed to say that that point of view 



had not occurred to him. He had imagined a blind 
person as surrounded by loving relatives, but chafing 
under the deprivation of the light of day. He had 
imagined himself being totally blind, and suddenly 
enabled to " watch " the day break and the sun rise 
by means of the new instrument. This reminder of 
the grim realities of the existence of the majority of 
the blind brought him back to earth. It also strength- 
ened his determination to persevere in the development 
of the instrument until those responsible for the 
welfare of the blind should be compelled to acknow- 
ledge its usefulness. 

After another twelve months of work he produced 
his first Reading Optophone, and showed it in action 
at the Birmingham meeting of the British Association 
on September 11, 1913. The following account 
appeared in the Electrician : 

" Last year I described 1 and exhibited at the 
London Optical Convention an apparatus for con- 
verting light into sound by means of electrical effects, 
and proposed the name * optophone * for such an 
instrument, as its primary object is not to transmit 
sound by means of light {photophone}, but to f see * 
by means of sound. In that original apparatus, 
two selenium * cells * formed two arms of a Wheat- 
stone bridge arrangement, and the equality of their 
resistances (and hence, of their illumination) was 
tested by means of a telephone in the * galvanometer 
branch/ the current through this branch being 
periodically interrupted by clockwork. The appara- 
tus enabled totally blind persons to discover the 

i I^ysOatescke Zetisckrift, 13, p. 942, October 1, 


whereabouts of windows, lights and bright objects 
by the ear alone. 

" The new * reading optophone/ which was shown 
to the honorary graduates and other British Associa- 
tion visitors at Birmingham University on September 
11, is a further development in the same direction. 
In this case, however, the light used is itself inter- 
mittent, and is indicated in the telephone by means 
of the current fluctuations due to the intermittent 
illumination of the selenium. 

" It is well known that the conductivity of selenium 
is capable of following fluctuations of light with 
extreme rapidity, as shown by the successes already 
attained in the photophonic transmission of speech. 
The ' instantaneous * change of conductivity under 
the action of light is approximately linear/ so that 
the amplitude of oscillation, with a given intensity 
of light, is nearly inversely proportional to^the fre- 
quency. This would mean that in converting light 
oscillations into telephone sounds the higher notes 
would be feebler than the lower ones. But this is 
largely counterbalanced by the resonance of the ear 
and of the telephone membrane, and it is found in 
practice that the maximum audibility occurs some- 
where about a frequency of l^OOO waves per second. 

" The reading optophone consists essentially of a 
selenium preparation illuminated by a line of Alight 
broken up into dots. The light of each dot is inter- 
mittent, and each dot has a different frequency. 
Thus, in one apparatus actually constructed, the 
frequencies of the eight dots composing a line 8 cm. 
long are in the ratio of the numbers of the diatonic 
scale, viz. 24, 27, 30, 32, 36, 40, 45, 48. Large type 
printed on gelatine or other transparent material, 
when interposed between the source of light and the 
selenium, breaks up the line into dots differing in 

1 Fonrnier d'Albe, oy n Soc. Proc., A 89, p. 79, 1913. 


tone according to the shape of the letter, and with 
a little practice the letters of the alphabet are easily 
recognised and * read 5 by the ear. 

" The arrangement adopted is shown in the 
diagram. The line of light is furnished by an Osram 
* striplite * of 100 c.p., which is concentrated by 
means of a cylindrical water lens upon a revolving 
perforated brass disc provided with eight circles with 
the numbers of holes specified above. The disc is 

JOQO. Volts., 



spun at about 20 or 30 revs, per second by means of 
an electric motor. The line of dots of eight different 
frequencies exist, therefore, just at the surface of 
the brass disc. As it is not feasible to bring the 
transparency to be 'read* into contact with the 
brass disc, the luminous dots are transferred to the 
upper side of a wooden partition by means of a set 
of glass rods with flat ends embedded in the wood 
opposite the luminous dots. The flat ends of the 
rods are flush with the surface of the board, and the 


transparency can be safely and conveniently slid 
across them, 

"The selenium bridge Se is mounted above the 
transparency with just sufficient clearance to allow 
for free displacement. The luminous dots trans- 
mitted by the type or other transparency impress 
their frequencies upon the selenium, and the latter 
gives a musical note corresponding to each dot, even 
when the beams of light overlap on to the same portion 
of the selenium. When that occurs with neighbouring 
notes, * beats * are heard, just as they are when 
neighbouring notes on the piano are struck together. 

" Since the only thing perceived is the alternation 
of the light and darkness, and since that takes place 
hundreds of times per second, the effect of light is 
instantaneous, and the * lag 9 or inertia so unpleasantly 
associated with selenium is entirely absent. 

" The smallest type successfully read so far is an 
inch high, photographed white as a transparency. 
But it is quite unmistakable. The two vertical 
strokes of H or M give a chaos of notes, the middle 
stroke of N gives a falling gamut, the three horizontal 
strokes of E give a chord, and the curved lines of 
and S give characteristic flourishes of sound. The 
alphabet of capitals can be learnt in about an hour, 
and once the sounds are learnt, the process of reading 
may become as rapid as that of reading by sight. 

" The selenium bridges used have a high resistance, 
amounting as a rule to several megohms. They 
require an E.M.F. of 1,000 volts for the best results. 
The telephones used were a pair of 4,000 ohms each. 

" Since type of any size whatever can be put into 
the shape of a white-on-black transparency by means 
of photography, and simultaneously reduced to the 
proper size, the reading of type by the blind is now 
reduced to a matter of photography. This has over 
the Braille type the advantage of being generally 


legible, though, it is doubtful whether in the matter 
of cost the optophone can as yet compete with raised 

" It is obviously desirable that ordinary black-on- 
white type, printed on paper, should be read opto- 
phonically. Some experiments I have made in this 
direction are very encouraging. A strip of slate 
long enough to cover the line of dots was cut out and 
perforated with holes so as to let the upper ends of 
the glass rods project just beyond its surface. The 
slate was covered with selenium and sensitised. A 
glass plate was laid over the wooden ' reading desk * 
and the glass rods, and a printed advertisement of 
large type was placed face downwards on the glass. 
The white paper produced a chaos of all the notes, 
which broke up into more or less well-defined notes 
as the black letters were passed over the rods. But 
the loudness and distinctness so obtainable were 
greatly inferior to what they are by transmitted light. 
Still, the solution is there in principle, and it is only 
a matter of making the type smaller and the effects 
louder and more distinct. The blind will then be 
able to read everything as well as the sighted. 

" Needless to say, any succession or combination 
of musical notes can be picked out by properly 
arranged transparencies, and I have succeeded in 
transcribing a number of musical compositions in 
this manner, which are, of course, only audible in 
the telephone. These notes, in the absence of all 
other sounding mechanism, are particularly puxe and 
free from overtones. Indeed, a * musical optophone/ 
worked by this intermittent light, has been arranged 
by means of a simple keyboard, and some very pleas- 
ing effects may thus be obtained, more especially as 
the loudness and duration of the different notes is 
under very complete and separate control. As this, 
however, was not the in* "mediate object aimed at in 


devising tlie optophone it need not be further enlarged 
upon here." 

It is interesting to note that the letters first read 
were made to give the full sound of all the notes on 
their vertical lines, just as they do in the latest type- 
reading optophone of the present day. But in 1913 
this result was accomplished by making " trans- 
parencies " of the letters. The Author remembers 
making transparencies of the initials of the President of 
the British Association (Sir Oliver J. Lodge) and three 
of its honoured guests (Madame Curie, Professor 
Lorentz, and Professor Axrhenius) and teaching them 
to read them with the optophone (Fig. 15a, p. 98). 

Immediately after the B.A. meeting the Author 
set to work on the final stage of the problem that 
of bringing ordinary printed matter which the 
blind call " ink-print " to distinguish it from " raised 
type ** within the range of the optophone. It 
proved a very formidable task indeed, as the amount 
of light to be " made audible " was two or three 
hundred times less than the amount actuating the 
first reading optophone. For not only was the type 
much smaller, and its area about a hundred times 
less, but it had to be worked with light reflected from 
paper, and diffused as well. 

The Author recognised that the only chance of 
catching sufficient of the diffusely reflected light to 
produce a useful audible sound was to bring the 
selenium detector close up to the type. This could 


not be done without intercepting the beam of light, 
unless the selenium detector was perf orated , and then 
the amount of light caught on the selenium would 
only consist of the rays reflected sideways. But 
having obtained an audible sound by means of a 
sensitive S. G. Brown telephone, he constructed a 
selenium tablet on slate with a hole in it just sufficient 
to receive a beam of a width corresponding to the 
length of a letter of ordinary type. Thus he obtained 
the first "type-reading optophone/ 5 which he ex- 
hibited before the Royal Society in May and June 
1914. The following is a report taken from the 
English Mechanic : 

" At the meeting of the Royal Society on May 28, 
Dr. E. E. Fournier d'Albe, in a communication en- 
titled * A Type-reading Optophone/ described the 
latest development of Ms instrument known as the 
optophone, by which it is claimed that it is possible 
to enable the blind to read ordinary newspaper type, 
it being necessary for them to learn a sound alphabet 
that is about as difficult to master as the Morse code. 
Dr. Fournier d'Albe reminded the Fellows that two 
years before he had shown how it was possible, by 
taking advantage of the variations produced in the 
electrical properties of selenium under the influence 
of light, to enable a totally blind person to appreciate 
differences in illumination : differences of light 
become sensible as differences of sound heard in a 
telephone. The new form of the apparatus consisted 
essentially of a rapidly-rotating disc, perforated like 
a siren-disc, with several concentric circles of holes. 
A Nemst lamp was placed behind the disc, with its 
filament stretched radially across the circles. The 


light, shining through the holes, gave regularly recur- 
ring flashes, which, when of suitable frequency, could 
be detected by means of selenium and a telephone. 
An image of this line of intermittently luminous dots 
was thrown upon the type to be read, and the light, 
diffusely reflected from the type, was received on a 
selenium bridge. As each dot had a characteristic 
note, the sound heard in the telephone varied with 
each variation in the reflecting power of the surface 
under examination. As the letterpress was moved 
on in the direction of the line of type, the sound 
changed rapidly with every change in the shape of 
the letters, and with some practice the type could 
be c read j by ear. By means of an ordinary 
high-resistance telephone receiver, type a fifth 
of an inch^high could be read. The effect became 
rapidly fainter as the type diminished in size ; 
but ordinary newspaper "type was readable with 
the help of a highly-sensitive Brown telephone 

"Dr. Foumier d'Albe's new form of instrument 
constitutes a very considerable advance on that 
which he showed last year in Birmingham at the 
British Association. It was then necessary for -the 
type to be about 2 in. high, and to be printed in a 
transparent medium on a dark ground. In further 
explanation of the method, it may be stated that it 
is possible for musical notes to be produced in the 
telephone by variations in the electrical current 
passed through the instrument, the varying resist- 
ances of the selenium giving rise to variations in the 
electric currents produced. Roughly, Dr. Founder 
d'Albe said, the sounds heard in the telephone em- 
braced an octave, and the recognition of them 
depended on the ability of the user of the instrument 
to recognise which of the notes which might be heard 
was omitted, the difficulty of learning the alphabet 


being comparable with the difficulty of learning the 
Horse code. 

Such was the stage at which the optophone had 
arrived when the war broke out, and for some years 
the energies of " civilised " humanity were concen- 
trated on mutual destruction. But the problem was 
completely solved in principle, and the Author could 




reasonably expect that those whose business it is to 
look after the interests of the blind would not let the 
invention perish. He had yet to learn that every 
human institution is by nature conservative and shy 
of innovations. 

One of the most effective ways of blocking the 
adoption of a new invention is to spread a report 
that a much better invention is shortly about to 


appear. Those who, like the late Sir Arthur Pearson, 
had spent their energies lavishly in collecting funds 
for books in raised type printed on the Braille system, 
were anxious lest the fame of the new instrument 
should make Braille appear obsolete and thus dry up 
the constant supply of funds necessary for the upkeep 
of Braille literature. The following note, which 
appeared in the Braitte Review for April 1915, either 
deliberately or unconsciously turns the tables by 
bringing forward a super-invention unsupported by 
any evidence except a letter from an anonymous 
American inventor, who obviously never tried the 
experiment he describes : 


" Attempts have been made from time to time to 
utilise the peculiar electrical properties of the element 
selenium for the purpose of enabling the blind to 
read ordinary letter press, It will be remembered 
that at the Conference last year, Dr. Fournier d'Albe 
of the Birmingham University gave demonstrations 
of his apparatus, the Optophone, which aroused much 
interest. By means of a powerful electric light the 
shadow of the ink-print letter is cast upon the plate 
of selenium which then emits varying sounds for 
the different letters. A specimen of this apparatus 
has since been acquired by The National Institute. 
We have now received particulars from America of 
a new instrument which, instead of converting the 
letters into sound, reproduces a much-magnified image 
of the letter in relief, which can then be recognised 
by touch. The following descriptive extract from 
the inventor's letter may prove interesting to our 


readers : f The device consists of an instrument which, 
being passed over the type,, reflects a magnified shadow 
of the type through a dark tube, by means of a lens, 
on to a plate of selenium through which a current 
of electricity is passing. Selenium varies its electrical 
resistance in different lights. Above, and fused to the 
selenium plate are numerous wires connected in the 
circuit with small electro-magnets. Where the 
shadow or image of the type falls on the selenium the 
electrical resistance is greater, so that the magnets 
connected to the shaded parts of the selenium plate 
are supplied with less current, making them weaker 
than those magnets connected to the more illuminated 
parts of the plate. The duty of the electro-magnet 
group is to attract small iron pins. These pins are 
arranged by spiral springs to fly down only to those 
of the magnets whose attracting force is sufficient to 
contract the spring, i.e. the magnets receiving the 
strongest current, which are those connected with the 
selenium where most light is thrown. The pins over 
the magnets in the shadows stand out in relief, so 
that whatever shadow is thrown on the selenium 
plate is reproduced by the pin heads over the magnet 
group, and may be traced with the finger tip/ " 

The absurdity of making an electromagnet actuated 
by a current through selenium strong enough to 
counteract " spiral springs " is obvious to anyone 
familiar with the properties of selenium, and the 
result would, even if successful, only substitute the 
finger for the infinitely more sensitive ear. Besides, 
it is well known that ordinary letters in relief are 
very difficult to read. Hence the superiority of the 
Braille dot system. 

But a more serious rival arose shortly afterwards 


in tlie person of Professor F. (X Browne, of Illinois, 
who tad spent many years in research on selenium 
and had, in fact, founded a " school " of talented 
research students. He had found a way of producing 
large selenium crystals which were supposed to be 
particularly efficient in producing current on illumina- 
tion. Three of these crystals he mounted in a box 
with a slit at the bottom, which was passed over 
large letters of ordinary type illuminated from above. 
Each of the crystals was separately connected with 
a battery and electric interrupter, but the three 
interrupters had different musical frequencies. It 
was, in fact, a combination of three " exploring 
optophones/' This combination Professor Browne 
called a " Phonoptikon." On a description appearing 
in the Scientific American of August 14, 1915, the 
Author made the following comments (November 27, 
1915) : 

" To ike Editor of the ' Scientific American 9 

" I find in your issue of August 14 an account of 
F. C. Browne's * Phonoptikon/ which is claimed to 
be an improvement on my * type-reading Optophone/ 
As both instruments are described as enabling totally 
blind persons to read ordinary type by ear, some 
remarks on the respective merits of the two instru- 
ments may not be out of place. 

"The phonoptikon uses the net extra current 
obtained from a selenium cell mounted in a Wheat- 
stone bridge when the cell is illuminated. This 
principle I adopted in my first exploring optophone 


(1912), but I discarded it on account of the slowness 
with, which selenium recovers from illumination. In 
the Reading Optophone I use the fluctuations of 
current produced by intermittent illumination, and 
thus I reduce the effect of lag to about 1-1 3 000 of 
a second. In fact, the response to light and to 
darkness is instantaneous. The available current 
is, of course, reduced in about the same propor- 
tion, so that sensitive telephone receivers of high 
resistance (8,000 ohms) have to be used. The tele- 
phone relay figured in my Royal Society paper I have 
also discarded, as it did not respond equally to 
different notes. 

" The claim to distinguish all the ordinary letters by 
means of only three components arranged vertically 
I can hardly regard as serious. In any case, I found 
six the mininmim number, and with these all letters 
could be distinguished. The greatest difficulty en- 
countered is to distinguish between ' u 5 and f n/ 
and even this was done without fail by Prof. Muirhead, 
of Birmingham, after ten minutes' practice. I see 
no advantage in moving the receiver over the printed 
page instead of vice versa. The great practical 
difficulty is to maintain a good alinement, and in 
the phonoptikon as illustrated I see no contrivance 
for doing so. In the optophone this is done on the 
typewriter principle. 

" The two advantages which I do recognise in the 
phonoptikon are the absence of clockwork for pro- 
ducing intermittent light, and the fact that blank 
white paper gives no sound. On the other hand, there 
is a complex mechanism for current interruption ; 
and the ' black y response, while making learning 
much easier, will not, in my opinion, sensibly affect 
expert readers. The difference is similar to that 
between various systems of shorthand, where ease 
of acquisition only tells in the first stages. Besides, 


it is in general more appropriate tliat white should 
give a sound, and not black. 

" Now that the problem of ordinary reading for 
the blind has been seriously attacked along two 
different lines (and with complete success along at 
least one of them), we may hope that the instruments 
may soon become generally available. Here in 
England the scarcity of Nernst lamps and high- 
resistance telephones, due to the war, has practically 
stopped the manufacture of the optophone for the 
present. But American inventors and manufacturers 
are entirely free to use its principle in any way they 
choose. The main point is that those dwelling in 
darkness should perceive the light. 

"I am greatly interested in F. C. Browne's re- 
searches on selenium crystals, which clear up some 
hitherto obscure questions of theory. If these 
crystals are much more effective as receivers than 
ordinary ' cells/ it will be valuable, but I find it quite 
possible to obtain ' normal galvanometric efficiencies * 
of 100,000 microhms per lumen under standard 
conditions (1 volt, 1 lux, and |- minute alternating 
exposure to light and dark) with cells provided with 
carbon electrodes. This is much in excess of the 
older results, and I should be glad to know whether 
the new crystals can surpass it. 
" Yours truly, 


When, some years afterwards, the Author met 
Prof. Browne at the Royal Society, the latter very 
freely and handsomely acknowledged the superiority 
of the optophone as a solution of the reading problem. 

But the real clash was to come. In February 1917, 
the Author constructed an optophone embodying 
further improvements, and demonstrated it before 


the Roentgen Society. He arranged various letters 
on cards, and showed that the cards could be shuffled 
and then read correctly by means of the optophone. 
He also invited the National Institute for the Blind 
to send some representatives to hear Tirm read a 
newspaper on the optophone, only stipulating that 
if he did it successfully., they should testify to the 
fact of his having done so. After some delays, the 
test took place on March 28, 1917. It was reported 
in The Times as follows : 


" At the Selenium Laboratory, 27, Maddox Street, 
W., yesterday. Dr. Founder d'Albe gave a demonstra- 
tion of optophone reading before a small company 
which included (here follow names of examiners and 

" Experiments with the optophone have previously 
been described, but the demonstration yesterday was 
interesting as being the first which has shown the 
reading of small type by ear. Mr. Stainsby chose 
as a test passage the second leading article from The 
Times of March 27. The inventor was blindfolded, 
given the article, which he inserted in the optophone, 
and he then slowly but accurately began to spell out 
the sentences. The reading was achieved without 
an error. 

" The speed attained was not more than tkree 
words a minute, but Dr. Fournier d'Albe believes that 
by practice a considerably higher speed can be 
attained. The line-changing mechanism places an 
outside limit of twenty-five words on the reader's 
progress. To use the optophone students have to 


learn its alphabet, wMch is a Mud of musical adapta- 
tion of the Morse alphabet. There are sound dots 
and dashes, but these are combined with a range of 
musical notes falling within the compass of an octave. 
The sounds are conveyed to the ear by a receiver." 

The actual passage the first piece of " ink-print " 
ever read by ear since the world began was the 
following : 


" The Report of the e Agricultural Policy Sub- 
Committee/ of which we published a brief 
summary yesterday, deals with one of the most 
important problems raised by the war, but re- 
lating to the future. The public and the " 

Having accomplished this unprecedented feat, the 
Author naturally expected congratulations and ac- 
knowledgments from his examiners. He was in- 
formed, however, that they would draw up a report 
in due course. 

The blow fell on April 14, when a letter purporting 
to emanate from Sir Arthux Pearson appeared in 
The Times and most other papers, to say that the 
test had been a complete failure as far as any utility 
was concerned. The Times letter ran as follows : 


" To the Editor of ' The Times ' 

" On March 29 you reported a trial of the 
optophone by Dr. d'Albe, who endeavoured to 


demonstrate Its practical value for the blind. I 
have it from Dr. d'Albe that he had practised 130 
hours on the optophone used. How far short he fell 
of his expectations the following extract from a 
report submitted to me by the four experts of the 
National Institute for the Blind, who attended the 
demonstration, and two of whom were blind men, will 
show : 

" ' The speed which the inventor was able to attain 
one word in one minute and a quarter would be 
utterly useless. Dr. d'Albe's contention that in- 
creased speed was purely a question of practice is 
not convincing, for our knowledge of the optophone 
leads us to believe that the speed must always be so 
slow, and the use of the instrument so nerve-racking, 
as to make the optophone of little or no value to blind 
people, whatever may be its use in other directions. 
But even assuming that a satisfactory speed could 
be obtained, the expensive character of the instrument 
would put it out of the reach of the average blind 

" It is to be most sincerely hoped that Dr. d'AIbe 
will in the course of time succeed in producing results 
from his ingenious invention which will render it 
worthy of serious consideration by those who have 
the interests of the blind at heart. 
" Yours faithfully, 

" President, National Institute for the Blind." 

224-6-8, Great Portland Street, W, 

The letter to the Lancet was even more sharply 
worded. It contained the passage : 

" I hope that Dr. Fournier d'Albe will now cease 
to issue misleading statements with regard to the 
practical value of the optophone as a means of 


enabling blind people to read. It can at present 
be only described as an interesting scientific toy/' 

Truih made the cutting comment : " It is a pity 
that newspapers should give currency to fantastic 
stories of this sort, which awaken hopes only to blast 

Had the most shameless charlatan and impostor 
made false and " fantastic " claims, which were 
blasted at the first test, he could not have received 
a more merciless punishment. It should, however, 
be stated in justice to the late Sir Arthur Pearson 
a noble benefactor of the blind that it was not he 
who wrote that letter, but a gentleman to whom he 
had delegated the use of his name for Press purposes. 

In any case, the opposition had unmasked its guns. 
After that smashing bombardment it might very 
well have happened that the delicate structure had 
been levelled with the ground, and the optophone 
lost and forgotten for perhaps many generations. 

In defence of his brain-child, the Author wrote in 
The Times (April 16) : 

" To the Editor of ' The Times ' 

" S ^ 

" In reply to Sir Arthur Pearson's letter in 

The Times of to-day, kindly allow me to state that 
I never considered it part of my business to acquire 
or demonstrate the maximum speed attainable in 
reading a newspaper by ear. That the optophone will 
enable a totally blind person to do this after, say, six 


weeks' practice is now definitely established, and, as 
I am the only person wlio can speak from experience 
of the difficulties encountered, I may assure Sir Arthur 
Pearson that practising or reading with the optophone 
is no more * nerve-racking y than reading wireless 
messages, and is, indeed, a very similar process. Sir 
Arthur Pearson's * experts ' do not state that I also 
offered to read type-written letters and even carefully- 
written manuscript by ear, but that they took that 
possibility for granted. I should be interested to 
know what further ' results * I am expected to 
accumulate single-handed before * those who have 
the interests of the blind at heart J will deign to 
consider them * worthy of serious consideration/ 
" Yours faithfully, 


27, Maddox Street, W., 
April I*. 

And in the Westminster Gazette (April 18) : 


" I notice in your issue of the 14th inst. a 
letter from Sir Arthur Pearson regarding the speed 
with which a newspaper can be read by ear with 
the help of nay ' optophone/ Before the last test 
was made, I expressly disclaimed having myself 
attained a speed of twenty-five words a "minute, though 
such a speed should be only a matter of practice. 
The supremely important thing, now established 
beyond cavil, is that any ordinary book or newspaper 
can now be read by totally blind people. In January 
of this year not a single line of newspaper had ever 
been read by ear, neither by me nor anybody else. 
I read an unknown passage from a newspaper article 


blindfold in presence of Sir Arthur Pearson's experts 
on March 28. I leave the friends of the blind to judge 
the true import of that achievement. 
" Yours faithfully, 


Selenium Laboratory, 

27, Maddos Street, London, W.I, 
April 17. 

But to most people the word of " Sir Arthur 
Pearson " was final concerning anything connected 
with the blind, and as the full weight of his name was 
flung at the unfortunate invention, its doom appeared 
to be sealed. 

But it was but the darkness which precedes the 
dawn. Although the Author's resources were ex- 
hausted, and himself thoroughly discouraged, help 
was on its way. It came in the shape of an ofier by 
a distinguished mining engineer, Mr. W. Forster 
Brown, to provide funds for the training of some 
blind pupils in optophone reading and for the construc- 
tion of a certain number of type-reading optophones. 
This generous and public-spirited offer, prompted 
no doubt, by the typical Englishman's sense of fair- 
play, proved the turning-point in the life of the 
optophone. It disappeared from the public view for 
over a year, and its opponents probably congratulated 
themselves on the success of their policy, but the 
final triumph was being quietly and steadily prepared. 

In June 1917, the Author met the Misses Jameson 
(Mary and Margaret) , daughters of Mr. Thomas 


Jameson, of South Norwood, who were both blind 
from earliest infancy, but had received a liberal 
education and were expert Braille readers. He 
arranged to give them a series of lessons in optophone 
reading, which began on July 4, 1917. They were so 
successful that after twenty lessons of an hour each 
they were able to read their first complete page of 
ordinary print. 

The optophone on which they read was provided 
with a gas-filled lamp of sixty candle-power, the 
filament being placed edge-wise to make it into a 
line of light. The instrument was not a portable 
one, so the lessons had to be given at 27, Maddox 
Street. When winter came, it was thought necessary 
to enable the pupils to continue practice in their own 
house 3 and several new types of a portable optophone 
were worked out. A very small motor was con- 
structed, which drove the light siren disc by means 
of a thread. The motor had to be carefully insulated 
so as not to interfere- with clear hearing in the tele- 

The instrument finally evolved by the Author, and 
provisionally placed on ike market by the Medical 
Supply Association at the price of 35, is shown in 
the accompanying illustration (Fig. 17), 

It was described as follows : 

"A small disc, D, is made to rotate rapidly by 
means of a minute electric motor, turned on by the 
switch M. The disc is provided with five concentric 
circles of holes, the numbers in successive circles 


being 24, 27, 32, 36, and 45 respectively (these corre- 
spond to the notes' C, D, F, G-, and B). ^ The disc is 
illuminated from below by a small electric lamp and 
condenser, turned on by means of the switch A. 
A slit found above the disc cuts out a radial portion, 
so that a line of five luminous dots is seen from above. 
A small image of this line is thrown upon the upper 
surface of the glass plate G, and is thus focussed upon 
any point laid flat upon the glass. The lamp, disc, 
and lenses are mounted on a carriage which can be 
moved from right to left by means of the handle BL 
The top of this carriage bears a selenium tablet, 
which is placed in circuit with a battery and telephone. 
The glass plate with its stand forms a book-rest, 
which will take any ordinary size of book or news- 
paper. This book-rest is moved to and fro at 
right angles to the printed line by means of the line- 
changing head L. This head moves with audible 
clicks, and by counting these clicks, the operator can 
make sure of getting the next line correctly into 

" The telephone receiver is worn on the head, as 
is done without discomfort by all telephonists and 
wireless operators. 

" Experience has shown that with good hearing 
(not necessarily a 'musical ear 5 ), the alphabet can 
be learnt in about eight hours , and easy words and 
sentences in clear type can be read after from ten to 
twenty lessons. The acquisition of speed is entirely 
a matter of practice. The English alphabet holds 
good for reading French, Italian, Spanish, Portuguese 
and a number of other languages. Other forms of 
type have, naturally, their own characteristic sounds, 
and must be learnt separately. 

" It is also possible by means of the optophone to 
read type-script, and as blind people can now use 
type- writers, it is possible for a business man to type 

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5a*to?d *Jfl!htttete 

, Mtti*iiM Tsta, ^ui*'*t* *[>MI 'T 

.4.E&K ^;to? ?lk , ; ,;; i '>^ 




a letter, read it over, and read a type- written reply. 

" Ordinary handwriting cannot be read by ear, 
unless it is written in careful imitation of type. 

" Incidental uses of the optophone consist in the 
examination of pictures, photographs, maps, and 
dress materials/' 

This was the optophone risen like a phoenix from, 
its ashes which came out into the world once more 
on August 27, 1918, at the British Scientific Products 
Exhibition held at Bang's College, London. The 
Author gave a lecture at which Sir Richard Gregory, 
F.R.A.S., Editor of Nature, presided. At the con- 
clusion of the lecture Miss Jameson gave a test reading 
from Dante's Inferno. A page was chosen by the 
audience. Miss Jameson put the book on the book- 
rest of the optophone and began to read. The words 
she read were: "in the light." " Is that all I" said 
the Chairman. " Yes/ 3 said the blind reader. 
" There are only three words in this line, with a full 
stop after them/' It turned out to be quite correct, 
and the words read seemed to many of those present 
to be very appropriate to the occasion. 

That test, followed by other public tests, was too 
powerful to be extinguished even by the magic of 
Sir Arthur Pearson's name. There was another 
eruption of Press notices, and another avalanche of 
inquiries descending on the various Blind Institu- 
tions. The Illustrated London News gave a page of 
cleverly drawn diagrams, two of which are shown 
above (p. 123). 

tmsttf m cwrwt 


(Se. No. 1) 

^ Battery of 
d|: small dry cells* 

1 1 -^L. silm n't ftfl vfrtf ?c 


Telephone, 1=1 

3 , 





Selenium Bridge 

(Se. No, 2). 




And Punch, quoting a war description from a 
Scottish, paper : " Not by straining Ms eyes to tie 
utmost could lie catch a sound/' remarked, "He 
should have tried the new optophone attachment/' 

But the most important event was the demonstra- 
tion given on August 30, at which Admiral Sir 


Reginald Bacon, then head of the Munitions Inven- 
tions Department, presided. Miss Jameson again 
read several lines faultlessly, and Six Reginald 
Bacon was so impressed that he communicated with 
Messrs. Barr and Stroud, Ltd., a famous firm of 
instrument makers, advising them to take up the 
manufacture of the optophone. 
That introduction proved of incalculable benefit 


to the optophone. Tlie wooden instrument on winch 
Miss Jameson gave the first public reading exhibition 
(now in the Science Museum at South Kensington) 
was rather fragile and could only be transported from 
place to place with difficulty. It required the com- 
bination of fine adjustment with strength and dura- 
bility such as would be supplied by the makers of 
Ban and Stroud's famous range-finders. 

The manufacture of the optophone was a matter 
which could not be undertaken as an ordinary business 
enterprise. The number of blind people capable of 
benefiting by reading is limited. It is true that 
nearly half-a-million has been spent on providing 
them with Braille literature, and large annual sums 
are still expended on it, but it was not at all certain 
that a similar spirit of philanthropy would provide 
them with an expensive instrument for unlimited 
reading, and individuals capable of supplying them- 
selves with it were few, and many of them were of 
an age unsuitable for acquiring a new accomplishment. 

Nevertheless, Professor Archibald Barr, F.R.S., the 
head of the firm, spent many months of work and 
large sums in redesigning the instrument, making 
it compact and portable and " fool-proof," and pro- 
viding it with some new contrivances and accessories 
which would render its use easy and safe even in the 
hands of an almost necessarily clumsy blind reader. 

In order to make the instrument compact, it was 
decided to employ a curved glass plate on the book- 
rest, so that the optical reading arm (called the 


" tracer **) could be pivoted instead of running on a 
slide. Tlie "tracer" was also moved down the 
page instead of mating the page movable. Moreover, 
an automatic movement of the tracer along the line 
was substituted for the rack-and-pinion movement 
originally used by the Author. The motive power 
was a spring, controlled by an oil governor of extra- 
ordinary range and efficiency specially invented by 
Dr. Barr (Mg. 19, p. 67). 

The accompanying illustrations show these features. 
But the most important modification, introduced by 
Drs. Barr and Stroud and the Author conjointly, 
was to make the black letters themselves produce 
the sound, instead of letting them blot it out. This 
was called the " black-sounding " system as dis- 
tinguished from the "white-sounding" previously 
used. The effect was to reproduce the sounds as 
produced by the first reading optophone of 1913 
(with large transparent letters). 

On March 24, 1920, Dr. Barr brought the finished 
instrument before the Royal Philosophical Society of 
Glasgow. By an ingenious arrangement of reed 
sounders he was able to give his audience a very good 
idea of the sounds of various letters and actually 
made them " read by ear " the sentences : ** Will 
Women Want to Yote ? Wait and See." 

In July of the same year, Dr. Barr had the honour 

of demonstrating the instrument personally to Their 

Majesties the King and Queen. This memorable 

event was reported by the Daily Mail on July 9, 1920 : 



"Their Majesties were able to test a new and 
wonderful device wMcli enables the blind to read, 
or rather to hear, translated into musical notes, any 
printed matter. Hitherto reading for the blind has 
been possible only by means of the special Braille 
type. By this new invention, called the optophone 
and Newington House is the first institution to acquire 
the apparatus literature is translated into music. 

" It is the invention of Dr. E. E. Fournier d'Albe, 
and has been modified and developed by Messrs. Barr 
and Stroud, of Glasgow, who make the giant heavy- 
artillery range-finders. In an ordinary telephone 
receiver is produced a series of musical notes, form ing 
tunes representing the various letters as they are 
passed over by the instrument in traversing a line 
of printing. 

" It renders all ordinary printed works, including 
typewritten matter, available to the blind, and it 
depends, not on touch, but on hearing, which is a 
peculiarly sensitive faculty with blinded persons. 
The music of the alphabet can be learned after a 
comparatively few lessons. 

"The King and Queen listened to the melody 
provided by a chapter of the Bible being passed over 
the instrument. The sound is soft and pleasant, 
rather like the notes of a banjo floating across the 
water. * It is wonderful/ was the King's comment." 

Almost immediately after this auspicious day, the 
National Institute for the Blind decided to purchase 
an optophone from Messrs. Barr and Stroud (the 
price was then 100 guineas) and to make arrangements 
with the Author for daily lessons in optophone reading 
to be given to two selected pupils. These lessons 
began in October and continued for six months, with 
a view to a test at the end of the period. 


On November 22 5 Messrs. Barr and Stroud pre- 
sented one of the new " black-sounding " instruments 
to Miss Jameson, who thereupon set to work to re- 
acquire her reading proficiency on a new system. As 
the system was still on its trial, whereas the " white- 
sounder " had already enabled her to read fifteen 
words per minute on the average, the Author decided 
to teach the N.I.B. pupils on the " white-sounding " 
system, particularly as the instrument as constructed 
can be worked on both systems (Fig. 20). 

On January 5, 1921, a lecture was given by Dr. Barr 
(and read by Mr. Morrison, the London Director of 
the firm) before a joint meeting of the Physical and 
Optical Society at South Kensington. Some extracts 
from the Morning Post report are here appended : 

" An astonishing demonstration of the advance of 
science was given last night in the Imperial College 
of Science, South Kensington. At a lecture given 
in connection with the exhibition of the Physical 
Society of London and the Optical Society, a blind 
girl read by telephone with perfect accuracy two lines 
of a book which had been selected at random. As I 
selected the page myself, and as Sir William Collins, 
a famous ^eye specialist, took an intimate interest in 
the experiment, I have no .hesitation in saying that 
its result was beyond dispute. A distinguished 
doctor put the thing in a nutshell His remark was, 
* It beats Maskelyne and Cooke/ 

^"Leaving out all technical details, of advancing 
discovery and apparatus made to fit the discoveries, 
the main principle of the new system is this : By the 
use of selenium it is possible when tracing a delicate 
instrument over printed paper to translate the differ- 


ences between white and black into musical notes, 
and the expert can transliterate each note into its 
appropriate letter, and spell out the words as they 
come out. The form of each letter causes it to sing 
its own little tune. They sound, at the first en- 
counter, as similar as the chords blown on a mouth- 
organ, but after some practice the diligent student 
can distinguish between them. Five cardinal notes 
come into play, and are indicated to the careful ear 
the lower G, and then the middle C, D, E, and G. 

" Put a printed page on the machine, work it at 
the desired speed, and the blind reader can spell out 
the words always supposing, of course, that he or 
she is good at spelling, for the optophone can do no 
more than represent the sound equivalent of the dark 
blotches, meaning the letters, it encounters on the 
body of the white paper. 

" The value of this new invention to people deprived 
of sight is enormous. Work for which the nation can 
never be too grateful has been done by the Braille 
and Moon systems of providing perforated reading 
matter for the blind but a Braille volume is twenty- 
five times the weight, and a Moon volume forty-five 
times the weight, of an ordinary printed book, and 
only one in ten thousand books is put into raised type 
for the finger reading of the blind. 

" At the lecture the audience were invited to select 
a passage from a school primer, to see whether a blind 
person could read it. Being a journalist, with special 
reasons for satisfying myself as to the efficacy of the 
test, I volunteered. The offer was instantly accepted. 
I picked out, at random, the first line of page 85. 
The page was taken out, and put on the machine. 
A blind girl, Miss Mary Jameson, who has been study- 
ing the system for five weeks, put the telephone 
receivers to her ears, and read the words, with abso- 
lute accuracy, at about the rate at which a telegraphist 


would convey a message. The book was passed 
further down the bench, and then another line was 
read, this also without a fault. 

" Mr. Francis Morrison, who read the lecture in the 
absence, through illness, of Emeritus Professor 
Archibald Barr, expressed the conviction that the 
reading of printed matter will be a real possibility for 
the blind in the future. 

" At my request Sir William Collins expressed his 
opinion on the matter. 

" ' I became interested in the optophone/ he said, 
' from seeing one of the earlier models which Dr. 
Fpurnier d'Albe demonstrated to me. I have watched 
with interest its subsequent evolution, and I believe 
it has a future. It demands the prompt apprehension 
of minute differences of motif, and a certain degree of 
intelligence, patience, and aptitude. It should open 
up resources to some blind persons which have hitherto 
been denied them. Even with a little practice the 
motif of different letters can be differentiated/ " 

This lecture and demonstration seems to have 
provoked the anger and alarm of the hidden opponent 
who wielded Sir Arthur Pearson's name (he was too 
ill at the time to attend to anything, and died, in fact, 
shortly afterwards). The following extraordinary 
correspondence ensued : 


January 6, 1921. , 

" To the Editor of the ' Daily Telegraph 3 


" My attention has been drawn to a statement 
that has lately appeared in the public Press to the 
effect that there is an instrument named the * Opto- 


phone/ the invention of Dr. E. E. Fournier d'Albe, 
of London, by means of which the blind can ' read ' 
ordinary print. It is claimed., moreover, that the 
Braille system will be superseded by this method, 
which is easy to learn. As this announcement is 
thoroughly misleading, and as, moreover, it may 
mislead hundreds of blind people, I trust you will 
find room in your valuable paper for this letter. The 
fact is that the National Institute for the Blind have 
been experimenting with the optophone for the last 
few months in order to ascertain whether an at 
present very intricate and expensive machine can 
in time be made of practical service to the blind. 
We hope soon to be able to report definitely as to 
the result of new investigations. Even if such a 
machine were ever to be made of practical value, to 
say that it would ever supersede the Braille method of 
reading is as true as to say that steam-rollers will 
ever supersede motor-cars, which is absurd, 
" Yours faithfully, 


National Institute for the Blind, 
Great Portland Street, W.I, 

The above letter also appeared in the Star, where- 
upon Miss Jameson wrote to the latter paper : 

" A paragraph in your ' " Star " Man's Diary * 
for Friday last has been read to me, in which Sir 
Arthur Pearson is represented as describing the opto- 
phone as incapable of * being made of practical service 
to the blind/ 

" I have been blind from birth. I learned Braille 
in my childhood, and I have recently taken part with 
credit in a public Braille reading-competition. I 
have also used the optophone, and I can therefore 


speak with some practical knowledge of the two 
contrasted systems. 

" With this knowledge I have no hesitation in 
saying that the optophone is of practical service to 
me. I have up to the present had just forty-eight 
hours' practice with the type of instrument I now 
use. In that time I have succeeded in reading an 
ordinary printed copy of some of Hans Andersen's 
Fairy Tales and also a Palmerston reader. 

" I am hopeful that the optophone will prove of 
great service to all blind people. In the meantime 
I am glad to be able to testify to the use that it has 
been to me/' 

The " Impearsonator " felt he had gone too far, 
and hastened to modify his attitude. The Star of 
January 12 contained the following : 

" Sir Arthur Pearson, President of the National 
Institute for the Blind, writes : 

Miss Jameson, the blind lady, whose letter 
about the Type-Reading Optophone appeared in 
your last night's^issue, stated that I had said that the 
optophone was "incapable of being made of practical 
service to the blind/' 

" ' What I said was : " The fact is that the National 
Institute for the Blind have been experimenting with 
the optophone for the last few months in order to 
ascertain whether an at present very intricate and 
expensive machine can in time be made of practical 
service to the blind." 

" * Do not let me say anything which will lead the 
public to suppose that I am throwing cold water on 
this machine, for it is a masterpiece of ingenuity, and 
in these days of rapid advance in connection with 
scientific matters no one can tell where it may lead. 


" * At the same time, do not let us raise the topes 
of the blind community by vague statements about 
blind people reading ordinary books/ " 

The last Parthian shot concerning " vague state- 
ments about blind people reading ordinary books " 
was truly amazing. The statements were not vague, 
but perfectly definite. Blind people can read ordin- 
ary books. They do read ordinary books. Where 
is the vagueness ? Or where is the exaggeration ? 

In any case, it was the last kick of the dying opposi- 
tion, that opposition which came so perilously near 
to wrecking the optophone for an indefinite time. 

Thereafter, one triumph succeeded another. On 
February 23, the Prince of Wales visited an exhibition 
at Olympia where the optophone was being shown, 
and took a short lesson in reading, In this connec- 
tion, an amusing event occurred. Wishing to hear 
clearly, the Prince sent a message to the Guards band 
in the gallery to stop playing. Misinterpreting the 
message, the bandmaster finished the performance 
by striking up the National Anthem. The Prince is 
said to have smilingly re'marked that he was a little 
premature ! 

In March a kinematograph film was prepared by 
the Gaumont Company to show the optophone in use 
at the National Institute for the Blind. That film 
had the honour of being shown to Their Majesties 
on the occasion of their visit to the Earl of Derby. 

About the same time, successful attempts were 
made to amplify the optophone sounds so as to make 



FIG. 23. 1FIG " 2C - 

25 SAME. 


BLIND (Gaumont Film). 


them heard by a large audience. The initiative in 
this matter was due to Mr. A. Campbell Swinton 
and Mr. G. P. MacCarthy. Miss Mabel Green, of the 
N.I.B., was able to read from the amplified sound, 
using the white-sounding system. 

On April 6, 1921, Dr. Barr delivered a lecture on 
the optophone before the Royal Society of Arts, 
Mr. Campbell Swinton being in the chair. The lec- 
ture was followed by a demonstration of reading given 
by Miss Green, and by a discussion which marked a 
considerable advance in the public treatment of the 

" The Chairman (Mr. Alan A. Campbell Swinton, 
F.R.S.), in opening the discussion, said the Author 
had mentioned the advantages and disadvantages 
of the optophone as compared with Braille and Moon 
type, and that reminded him of a story he had been 
told a few days ago about an elderly gentleman who 
was losing his sight and therefore was learning to read 
Braille. He said the great advantage of Braille was 
that in cold weather one could read in bed and still 
keep one's hands under the bedclothes. He was 
afraid the optophone was not perhaps adapted for 
that ! He was also reminded by the Author's 
remarks of an interview he had some years ago with 
Prof. Graham Bell, the inventor of the telephone. 
Prof. Bell said to him on that occasion : ' You know 
people think that I am an electrician, but I am not. 
On the other hand, one of my friends said I could not 
be an electrician, because if I had been I should 
have known beforehand that my telephone could not 
work/ He thought perhaps that remark had some 
bearing upon Dr. Fournier d'Albe's wonderful inven- 


tion, because lie did not tMnk any electrician would 
have believed it possible to make the optophone work 
certainly not to make it work in the wonderful 
way that had been achieved by the Author. 

"Mr. Henry Stainsby (Secretary-General of the 
National Institute for the Blind) said that since the 
year 1914 he had been very much interested in the 
optophone. It was in that year, just before the out- 
break of the war, that Dr. Founder d'Albe gave an 
exhibition of the optophone at a very important 
International Conference on the blind, which was held 
at the Church House, Westminster. As the Author 
said, the subject remained in abeyance for a long 
period, in consequence of the war, but had now been 
revived, and the Institute with which he was connected 
had taken an active part in testing the apparatus and 
in affording facilities for instruction in its use. At 
the request of the Inventions and Research Com- 
mittee of the Institute he had undertaken to make 
the tests, but they were not yet completed, so he was 
not in a position to give the results of them, and the 
remarks he was about to make were, therefore, 
personal and not official. He had come to the con- 
clusion that the optophone had not yet had a fair 
test. The human material that had been used had 
not been of the right kind. People were taught to 
read in the ordinary way very early in life, and he 
was convinced that if the optophone was to be pro- 
perly tested, the tests should be carried out in a school 
amongst young children, and should extend over 
a long period. If that plan was adopted he was very 
much inclined to think that the results would surpass 
general expectations. The Author had mentioned 
the Braille and Moon type, in both of which types the 
National Institute for the Blind published the bulk 
of the literature issued for the blind in the whole 
world. The Moon type did not occupy quite so 


mucli space as the Author thought; indeed, not 
quite half as much ; nevertheless, both the Braille 
and the Moon types were extremely bulky. The 
great advantage of the optophone was that it put the 
literature of the whole world at the command of the 
blind, whereas tactile print gave them a very limited 
field indeed. Therefore, if the optophone proved a 
success, as everyone sincerely hoped it would, a great 
deal more reading matter would be put at the com- 
mand of the blind than was at present available to 

" The Hon. Sir Charles A. Parsons, K.C.B., F.R.S., 
in seconding the vote of thanks, said the optophone 
embodied more physical inventions and properties 
of matter than almost any instrument he had ever 
seen. It provided a beautiful means of linking the 
musical gamut with the altitude of the letters. A 
musician could, by reading music, appreciate its 
beauty and harmony from very long experience 
beginning at an early age, and in the optophone there 
was the transfer of letters into the altitude of the 
* doh, ray, me, soh ' gamut. He remembered once 
hearing that some Japanese were buried in a grave- 
yard at Newcastle-on-Tyne, and they had a tombstone 
with an inscription in Japanese letters > and two pit- 
men happened to go by it one day. One asked the 
other if he could read it, and he replied : f No, but 
if I had my fiddle I might play it ! '' The optophone 
contained some most beautiful mechanical devices. 
The whole mechanism, in fact, was perfectly wonder- 
ful, and the governor was quite original. He was 
sure everyone present was very much indebted to 
the Author for explaining the instrument so very 
lucidly. He thought the principles involved in it 
were probably capable of very great enlargement 
and elaboration in the future, and it might be made 
to reproduce music in the same way as it read printing. 


" Mr. Archibald Ban, LL.D., D.Sc., in reply, said 
it had been a great pleasure to him to have interested 
those present in the optophone, which he thought 
had considerable possibilities before it. Dr. Fournier 
d'Albe had referred to the perforations on the disc. 
That disc was made by the very simple process of 
drawing a picture of the disc, photographing it upon 
the metal, and etching it through. In that way it 
had been possible to make the disc exceedingly true, 
of a very thin light material, and at a reasonable cost. 
Dr. Fournier d'Albe had also said that Miss Jameson 
had been able to read French by the optophone, and 
he might mention that Miss Jameson told him that 
she thought French characters were more easy to 
read than English, on account of the accents. She 
found the accents an advantage rather than a dis- 
advantage. With regard to Miss Green's demonstra- 
tion, the speed at which she had read on the present 
occasion must not be taken as her best speed, partly 
on account of the circumstances and also for the 
reason that whereas with Braille one could speak and 
feel at the same time, one could hardly listen and 
speak at the same time, as was necessary in reading 
aloud with the optophone. In connection with the 
remarks Sir Charles Parsons had made about the 
automatic gear controlled by a governor, he "might 
say that the instrument had a little spring which 
had very considerable difference of driving power, 
and the tracer had very considerable weight. The 
arrangement was such, however, that when the 
spring was strong the tracer had to be raised and when 
the spring became weaker towards the end the tracer 
helped it. The result was that a uniform torque was 
obtained, which caused the instrument to be driven 
at a uniform speed/ ' 

On April 14, Miss Jameson gave a demonstration 


in Paris, when she performed the seemingly wonderful 
feat of reading French. It so happened that the 
chief French periodical published in the interests of 
the blind, L'Ami des Aveugles, had published (Febru- 
ary 1921) a criticism of the optophone on the ground 
that an automatic machine could never be used for 
the " infinite variety " of type to be found in books. 
The result of Miss Jameson's visit was a cordial 
amende in the April number. It said : 

" Endowed with a bright intelligence and charming 
grace. Miss Jameson victoriously replied to all our 


PIG. 37. 

objections. She easily read with the optophone a 
line chosen at random in the Ami des Aveugles which 
we gave her to read without preparation." 

When the official report of the N.I.B. appeared, it 
was found that the main question at issue can the 
blind read by ear ? was at length officially answered 
in the affirmative, while the question of speed was 
left open. The salient passages of Mr. Stainsby's 
report are given below : 

" I have tested Miss Green's reading on the opto- 
phone on seven different occasions, each test being 
of thirty minutes* duration and on * unseen matter/ 


" (1) Extract from Heroes of the Darkness, eighty- 
five words in thirty minutes, say three 
words per minute. 

" (2) Extract from leading article of Daily Tele- 
graph, sixty words in thirty minutes 
two words per minute. 
" (3) Extract from Optimism : 

" Test (a) Eighty-nine words in thirty 

minutes, say three words per minute. 
" Test (6) Seventy-eight words in thirty 
minutes, say two-and-a-half words per 

" Test (c) Sixty-four words in thirty min- 
utes, say two words per minute. 
" (4) Extract from The World I Live in, sixty-five 
words in thirty minutes, say two words 
per minute. 

" (5) Extract from Pier's Plowman Histories, 
Junior, Book II, one hundred and nine- 
teen words in thirty minutes, say four 
words per minute. 

" It will thus be seen that the average speed is 
under three words per minute. Although slow the 
reading was accurate, very few words being unread 
or miscalled. Short and easy words of frequent 
recurrence were read with comparative ease, the 
reader evidently taking the word as a whole without 
analysing into letters. This is borne out by the last 
test, which was from a junior school book in everyday 
English. Long and uncommon words, particularly 
those containing little used letters as 'z/ caused 
much delay and consequently brought down the 
averages. Towards the close of a test the reading 
became slower, demonstrating the fact that until it 
becomes mechanical it will be tiring. This was 
obvious in the last test, when Miss Green read the 
first twenty-four words in four minutes, or six words 


per minute. This condition exists in a very marked 
degree in tactile reading, learners always being re- 
commended to take their lessons in small * doses/ 

" Notwithstanding this, I am assurred by Miss 
Green that she does not experience any tired feeling. 
Further, she assures me that the process of listening 
neither prevents her from grasping the full import 
of what she has read nor detracts from the enjoyment 
which she ordinarily gets out of reading. 

"Miss Green manipulated the instrument quite 
unaided, and occupied less than two minutes in 
placing her book in it ready for reading. 

" I am informed by Mr. Emblen, the other opto- 
phone student, that my tests, while perfectly fair, 
do not do justice to Miss Green. This is doubtless 
due to the fact that examinations of all kinds rarely 
show the examinee in the best light. 

(e In preparing this report I have had two main 
issues in mind, all others being in my judgment quite 
subordinate to these two. The first is, can blind 
people read ordinary ink-print matter ? The reply 
to this is emphatically yes. The second is, can they 
read at a speed which would make it worth their 
while to adopt the optophone as a reading instrument ? 
On this point I have already shown that speed is 
slow, but as a set-ofi against this it should be borne 
in mind, first, that no one has had adequate practice 
upon it, and secondly, that the right type of learner 
has not been tested. After mature consideration I 
have come to the conclusion that tests should be 
made on young children in a school for the blind, 
and that the same facilities should be afforded them 
as for tactile reading. In the latter this period ex- 
tends over a number of years, and fluency is only 
attained after long practice. While I am inclined 
to think that tactile reading will be more easily 
acquired than reading by means of the optophone, 


it must be borne in mind that the literature available 
through the former is relatively small, but through 
the latter world-wide and unlimited/' 

The examination on which this report was based 
had been conducted by Mr. Stainsby with the most 
scrupulous fairness. It was published in St: Dunstan's 
Magazine and subsequently issued in pamphlet form. 

Miss Green's practice had extended over one hun- 
dred and twenty hours, which should have given her 
a speed of six words a minute, it having been found 
that the number of hours divided by twenty gives 
the approximate speed in words per minute. As a 
matter of fact, she often attained speeds of fifteen 
or even twenty words per minute, but important 
examinations are very special occasions ! 

The main question being now decided in favour 
of the optophone, it remained to prove the speed 
of whicli it was capable. This has since been done 
by Miss Jameson, in a manner far beyond the in- 
ventor's most sanguine expectations. 

In July 1922, Miss Jameson attended the Congres 
National pour I* Amelioration du Sort des Aveugles in 
Paris, and presented a report on the optophone, 
written in excellent French, which was well received 
and subsequently published in full. 

On April 14, 1923, she visited the War Invalids' 
Exhibition at Brussels, and gave test readings in 
French and English in the presence of the Queen of 
the Belgians, who is herself the daughter of a Royal 


Finally, in June 1923, she gave a demonstration at 
an exhibition organised by the National Institute for 
the Blind, where she read at the rate of sixty words 
a minute, to the amazement of the officials present, 
some of which may have been among the former 
opponents of the optophone. 

Even that record was surpassed at the meeting of 
the British Association in Liverpool, where on one 
occasion her speed attained eighty words a minute. 
There seems no reason why she should not eventually 
attain the speed of eye-reading, which is about two 
hundred words a minute. (See Fig. 29, p. 68.) 

She says : " I read without spelling the words. 
I read words and sometimes whole phrases as such. 
The first book I read from cover to cover was 
Anthony Trollope's The Warden, a volume of the 
Everyman Series. The second was Hawthorne's 
Scarlet Letter. I also borrowed Knowlson's Art of 
Thinking from the Croydon Library and read it right 
through. It gave me a great deal of pleasure/ 3 

In the United States the optophone was first 
introduced by Mrs. Edward C. Bodman, of New York, 
who took a special interest in blinded soldiers. At 
least one pupil has learnt to read there, and given 
satisfactory demonstrations, but there are as yet no 
teachers available. 

And there we must leave the optophone for the 

present. It forms a romantic chapter in the history 

of the applications of science to the welfare of 

humanity. Scientifically speaking, the problem of 



reading for the blind is completely and finally solved. 
The constructional problem is also solved in a most 
satisfactory way. It remains to reduce the cost of 
production in order to bring it within the reach not 
of the average blind, for that is impossible but of 
those organisations and institutions which are 
founded to supply the needs of the blind. Above all, 
there must be an organisation for training and supply- 
ing teachers. But those matters are for the philan- 
thropists and public bodies ; and are outside the 
scope of a scientific work. 



WHEN, forty- three years ago, Graham Bell, the 
inventor of the telephone, transmitted speech for 
three hundred yards along a beam of light, a new era 
of human communication seemed about to come upon 
the world. The feat was worthy of a man of con- 
summate genius, whose ability seems never to have 
been properly appreciated. 

The method which he used to impress speech vibra- 
tions upon a beam of light was highly ingenious and 
extremely simple. He spoke into a funnel closed by 
means of a thin glass diaphragm coated with silver. 
In the course of its vibrations, the flat diaphragm 
became alternately convex and concave. If a beam 
of parallel light was thrown on the diaphragm, it 
was only transmitted in its entirety to a distance 
when the mirror was flat. Any convexity or con- 
cavity reduced the amount of light received at the 
distant station. Speech thus produced an alternation 
of light and darkness, and this alternation was faith- 
fully reproduced by selenium at the receiving end. 
Bell used a parabolic mirror and a cylindrical selenium 
cell made of circular brass plates insulated with 



mica. He also experimented with, a number of other 
receivers such as lampblack and other forms of 
carbon. He called liis apparatus a " photophone " 
(light-sounder) , a word which is very appropriate 
and easily distinguished from the optophone or 
" sight-sounder/' 

When, g in the beginning of the present century, 
Simon and Duddell invented the Speaking Arc, an 
opportunity was given for a new departure in the 
photo-transmission of speech. They put a trans- 
former in the circuit of an arc lamp and a telephone 
transmitter in the secondary circuit of the transformer. 
On speaking into the transmitter, slight fluctuations 
were imposed upon the arc, which " spoke " the 
words with the speaker. The fluctuations thus heard 
were accompanied by fluctuations of the arc-light, 
and these, when received upon a selenium cell at a 
distance, reproduced the original speech. 

An experiment for demonstrating this effect is 
shown in Fig. 30. Acetylene is admitted through 
the tube A into a chamber separated from the mouth- 
piece M by a thin diaphragm of rubber or gold- 
beater's skin. On speaking into the mouthpiece 
the flame fluctuates, and intermittent light falls on 
the selenium cell B. On connecting a battery and 
telephone receiver to the terminals C D the speech 
may be heard in the telephone (which may, of course, 
be at the end of miles of telephone wire). The light 
can be transmitted by a concave mirror or lens over 
a considerable distance, but the range is limited 


by the comparatively small intrinsic "brilliancy of 

Ernst Ruhmer, the German inventor who died just 
before the war, succeeded by means of the speaking 
arc in transmitting speech over a distance of six miles. 


His experiments were conducted on the " Wannsee " 
near Berlin. 

During the war the Author developed a method of 
transmitting Morse signals invisibly along a search- 
light beam, but the most useful work was accom- 
plished by Professor A. 0. Rankine, of South 
Kensington, who, in conjunction with Sir Wm. H. 
Bragg, devised an entirely new method of impressing 
speech variations upon a beam of light. It was done 


by utilising tlie vibrations of a mirror attached to tlie 
needle-clip of a sound-box as used in the gramophone. 
The needle vibrates over an angle of about a quarter 
of a degree, and it was necessary to find a way of 
concentrating an intense beam of light on the mirror 
and making its movement produce the necessary 
complete fluctuations. To solve this problem, Pro- 
fessor Eankine conceived the idea of transmitting an 
arc-light through a lens pasted over with a number of 
parallel strips of paper, forming a sort of grating. 
The small mirror was chosen of a focal length equal 
to half the distance between itself and the grating, 
so that an image of the grating was formed at the same 
distance from the mirror. This image fell upon a 
similar grating stuck on a lens of twice the focal 
length of the mirror, so that it could act as a search- 
light projector. In a state of rest, the image 
coincided with the second grating, and light was trans- 
mitted through half the surface of the second lens. 
But when speech entered the sound box, the vibra- 
tions of the mirror led to a rapid series of extinctions 
of the light, by the dark portions of the image coincid- 
ing with the transmitting portions of the second grid. 
The light was thus made intermittent in accordance 
with the sound vibrations, and could be received on a 
selenium cell, and reconverted into sound. 

On this principle, with some improvements in 
detail, Eankine constructed a new photophone which 
was extensively tested during the war in the Firth 
of Forth. Speech was transmitted in both directions 


between Hawkcraig and the island called Inchcolm, 
using tlie Author's selenium cells (" B " type) at 
both ends. A grid-photophone of this kind was 
shown in action at the British Association meeting 
at Liverpool in September 1923, the stations being 
at St. George's Hall and the Technical School respec- 

The photophone works best with the aid of sun- 
light, which has a greater intrinsic brilliancy than any 
terrestrial source. Its utility in desert and tropical 
countries where perpetual sunshine can be counted 
upon is obvious, and so are its advantages over wire- 
less telephony so long as the latter cannot be made 

Professor EanMne has lately constructed a photo- 
phonic microphone for use in wireless telephony. 
It has certain advantages over the carbon micro- 
phone which he explained as follows in a recent 
interview : 

" In the more recent developments of telephony, 
especially wireless telephony, and broadcasting in 
particular, the original sound energy has perforce 
to undergo in the process of transmission so many 
transformations and amplifications, each with its 
own liability to introduce distortion, that the accumu- 
lated effect on the final reproduction may reduce it 
to incomprehensibility. If, in addition, as is now a 
common practice, loud speakers with their admitted 
imperfections, are employed, distortion is still further 

It is evident that, in these circumstances, it is not 


safe to begin with anything but tlie best. In a broad- 
casting station expense and complication of apparatus 
are relatively unimportant matters ; the chief thing 
is to put into the transmitting valve as accurate as 
possible an electric copy of the sounds it is desired 
to broadcast, so that something more than occasional 
recognition of words may survive the subsequent 
series of distortions. 

" It is in this connection that the carbon microphone 
is finding its rivals, and, in some broadcasting stations, 
being abandoned in favour of them. I cannot do 
more than mention some of the various possible 
substitutes, the function of which, as we have seen, 
is to control accurately electrical power by means of 
sound vibrations. Curiously enough, one method 
which is attracting considerable attention is a rever- 
sion to the principle of Graham Bell's original trans- 
mitter, which used to serve the double purpose of 
transmitting and receiving. In this the electric 
currents are produced by the inductive action of the 
magnetic material of the diaphragm vibrating close 
to the coils surrounding the fixed magnet. Then 
there is the photophone, in which the sound vibrations 
control, first of all, a beam of light, which, in turn, 
through the agency of a selenium cell, operates an 
electric current. 

" In both of these the fluctuating currents are feeble 
compared with those obtainable by means of the 
carbon microphone, and have to be amplified by 
thermionic valves before application to the trans- 
mitting valve, but the results are of very distinctly 
superior quality. The photophone microphone, if 
I may so call it, is actually in use at the Manchester 
station/ 5 

It may be confidently anticipated that a simple 
photophone transmitter of the Rankine type, easily 


installed at any stations within siglit of each, other, 
and so closely directed that the messages can be 
received at one window of a house and at none of 
the others, will soon form one of the ordinary means 
of telephonic communication. 



THE conversion of light into sound and its recon- 
version into light immediately suggests the possibility 
of reversing the process., and beginning and ending it 
with sound. The recording and reproduction of 
sound is, of course, as old as Edison's phonograph, 
which he invented in 1874. But the various efforts 
hitherto made to reproduce a sound simultaneously 
with the visible action accompanying it have not 
succeeded satisfactorily on any method involving the 
phonograph or gramophone. The reason is not far 
to seek. The Kinematograph works with a continu- 
ous film usually moved at a certain rate by hand. 
The gramophone works mechanically, and if the 
sound is to accompany the action there must be 
perfect synchronism between the two mechanisms. 
It has been found impossible to secure this, although 
some very wonderful results were achieved, notably 
in the " Kinetophone " and the " Kane-Opera " 
shown in London some fifteen years ago. 

In 1908, Ernst Kuhmer invented the " Photo- 
graphophone/' which recorded the sounds of the 
speaking arc on a moving film in the shape of a 



" ladder " closely resembling a spectrum traversed 
by Fraunhofer lines (see Fig. 31, p. 93). On passing 
this record over a slit traversed by a beam of liglit 
and provided with a selenium cell, Eaihmer was able 
to hear the original sound accurately reproduced, 
through no other mechanism than that of light and 
the telephone receiver. 

Many other attempts in the same direction followed 
this first effort. Grindell Matthews in England and 
Professor Berglund in Sweden attained good results , 
the former adopting the ingenious device of photo- 
graphing the sound record on the margin of the film 
itself, so that a perfect synchronism was necessarily 
maintained. Strange to say, both these pioneers 
used a sort of wave-record, the amplitude of the wave 
not being shown by the intensity of the photographic 
blackening but by the extension of the wave at right 
angles to the margin of the film. One cannot help 
thinking that any success obtained in that direction 
was a more or less secondary effect. 

A first-class inventor who has lately taken up the 
same problem is an American, Mr. Lee de Forest, 
who invented the triode valve or Au&ion in 1912, 
thereby inaugurating the new wireless era which 
replaced the era of crystals and electrolytic detectors. 

Instead of using a speaking arc, Mr. de Forest 
uses a small cathode ray tube which he calls a 
" Photion." 

A vivid account of the new process was given in 
an interview with the inventor recently published in 


the Wireless Review, from wliicli we quote the follow- 
ing extract : 

" Perhaps you liave seen lately some of the neon- 
filled glow lamps which, are being used to attract 
attention in stores and shop windows. A tube of 
bent glass, often shaped into words or letters , contains 
a little of this neon gas, about one-thousandth of 
1 per cent, of which is contained in ordinary air. 
When a high-frequency electric current is sent through 
this neon-filled tube, the gas glows with a soft reddish 
light which is pleasant and attractive. The photion 
works on much this same principle. Of course, the 
gas in it is not neon, and the glow is violet, not red. 
But it, too, is a gas glow excited by an electric current. 

" If you watch carefully the glow of a photion in 
operation you may be able to see that the fight is not 
absolutely constant. It flickers a little. Pulses of 
greater brightness alternate with brief instants when 
the glow is a trifle dimmer. This means that the 
photion is translating sound into light. The rapid 
flickers and pulses which you see mean that you are 
literally seeing speech. 

" The photion tube is excited by a high-frequency 
electric current, modulated by the voice in exactly 
the same way as in a small radio-telephone trans- 
mitter. This part of the apparatus is in fact identical 
with the radiophone transmitter. 

" In the electric circuit which operates the photion, 
and which causes it to glow, we insert a highly special 
substitute for the microphone and one or more 
vacuum tubes as amplifiers. This receiver picks up 
sound waves and converts them into pulses of elec- 
tricity. The electric pulses, after being amplified 
sufficiently, control the radiophone which is exciting 
the glowing photion and affect its light. The flicker- 
ings of this light, its rapid brightenings and dimmings, 


correspond exactly to the waves of sound wMcli enter 
tlie microphone. 

" This shows you how the phonofilm process trans- 
forms sound into light ; but how does it photograph 
them, how do we secure a permanent record of them 
on the motion-picture film ? 

" This is how. The glowing photion is in a little 
chamber by itself inside the camera, and this chamber 
is light-tight except for one tiny slit only one milli- 
metre long and a fortieth of a millimetre wide. The 
moving film on which the motion picture is being 
taken runs past the photion chamber in such a position 
that the edge of the film passes just under this slit. 
The light from the photion streams through the slit 
and is photographed on the film, making the strip 
of tiny hair-like lines already described ; a darker 
line for each instant when the photion is brighter, a 
less dense line when the light of the photion is a little 
more dim. 

" This little ladder of lighter and darker lines is 
our photograph of sound, our answer to the problem 
of recording successfully both the sight and the 
sound. The width of the sound photographs is 
always the same. The intensity of the light, and 
that alone, is varied by the sound. This feature 
distinguishes the phonofilm from all other methods, 
and permits a more faithful reproduction of every 
light and shade of sound than is otherwise possible. 
And by this photion or phonofilm method, it is seen, 
there is complete absence of any mechanical moving 
parts, nothing in the entire system up to the final 
diaphragm of the loud-speaker which can introduce 
a natural period of vibration of its own, tending to 
distort the original sound, in recording or in repro- 
duction. So far as the taking of the moving picture 
is concerned, this is the whole of the story. 

" But how is one to get this back into real sound 


again ? How is the sound record on the film to be 
reproduced when the motion picture is run off in the 
theatre ? 

" Consider, first, what the problem is. The taking 
of the talking motion picture involved two successive 
conversions of one kind of vibration into another kind. 
First the waves of sound were converted into electric 
waves by the microphone. Next the electric waves 
were converted into light by the photion. Now we 
must do these same two things in reverse order. On 
the finished film is our little ladder of darker and 
lighter lines. A ray of light can be made to shine 
through this ladder, and the strength of the light 
that gets through will correspond to the lines on the 
ladder. As each dark line passes across, the light 
transmitted will be momentarily dimmer. This gives 
us, to start with, what we finished with when the 
moving picture was taken, namely, a light which 
flickers in exact correspondence with the waves of 
sound. The problem is to convert these flickers 
back again into real sound." 

Mr. de Forest prefers to use photo-electric cells for 
the reconversion of the record into sound. It is, of 
course, one of the possible ways of doing it, though 
the Author is inclined to think that it is not the 
most effective. 

Professor RanMne has also succeeded in repro- 
ducing speech from a film on which he took records 
of words as produced by his grid photophone. Three 
of these beautiful records, those of the words " Beet/' 
" This," and " Man/ 5 are reproduced in Fig. 31, p. 93. 

It will be noticed hotMfc " ladders " change in 
character along the strips. The closer texture of the 


third record is due to tlie strength, of bhe first overtone 
contained in the vocal a. 

Although, the problem of the Talking Film is thus 
practically solved, Mnema managers are doubtful 
of its popularity. They say that Mnema acting is 
independent of sound. It is an art in itself, and would 
not be benefited by introducing sounds which are 
not required. It would also reduce the number of 
good Mnema artistes considerably if only those with 
good voice production (and a good accent !) could 
be employed. And lastly, the Mnema film would 
no longer be the international thing it is now, easily 
adapted to any country by putting in the " legends JJ 
in the language of the country where it is shown. 

The utility and the promise of the Moon-element 
are by no means fully revealed as yet. It is unsur- 
passed in its function of producing electric currents 
from light. It is the supreme bridge between two 
of the most vital forms of energy. It enables us to 
convey our thoughts and our will along the highway 
of the ether of space. The coming generation will 
see signs and wonders which at present we can only 
surmise, but which will eclipse the marvellous results 
already achieved with the help of the Wonderful 



FOE use in connection with the transit telescope belonging 
to Binningliain University a special selenium bridge was 
prepared consisting of a narrow line of sensitised selenium 
on porcelain, mounted on ebonite so as to fit into the 
eyepiece end of the telescope. The line was 4 mm. 
long and 0*5 mm. wide, and it was placed 3 mm. behind 
the middle crosswire of the instrument, and parallel to 
the crosswire. The focal length of the objective being 
30 inches, the transit of an equatorial star across the 
selenium gap occupied 9*0 seconds. The aperture used 
was 2 inches. The selenium bridge, whose resistance 
was about 20 megohms, was inserted in an accumulator 
circuit giving 50 volts, and containing one coil of the 
Thomson differential galvanometer used before. A com- 
pensating current was sent through the other coil. The 
magnetic field was adjusted so that the galvanometer 
gave a deflection of 320 divs. per micro-ampere. The 
swings were damped, when necessary, by means of an 
adjustable resistance in the compensating circuit. 

The results are given in the following table. The 
smaller deflections were practically aperiodic. In the 
case of the larger ones (Spica and Arcturus) the aperiodi- 
city was secured by artificial damping. The efficiencies 
obtained were so much in excess of those obtained before 
that they are best expressed in ohms per lumen instead 
of microhms per lumen. The faintest illumination of 
the objective lens was 0*0078 micro-lux, but as the light 




s B 


















































































o 3 




















i i 










. i 






















? l 

















^Q r? 



























o . 









f ' 

1 ' 












S3 * 





bion of S 













-r> V3 

















is concentrated upon a disc 62,000 times smaller in area 
than the objective, the faintest actual illumination of 
the selenium was as high as 485 micro-lux. As the Se 
bridge used showed very little inertia, it may be safely 
assumed that the deflections observed are a measure of 
the " final " deflection. In any case, the original resist- 


C f V ( 


ance was recovered within a few seconds after the transit 
had taken place. 

The above diagram shows the relation between the 
difference of conductivity and the square root of the 
illumination. It is seen that the relation is a linear one, 
thus confirming the results obtained with small artificial 

It may be added that it was found possible to make the 


light reflected by the galvanometer mirror impinge upon 
a second Se bridge, and so reduce the resistance of the 
latter sufficiently to work a relay. In this way, auto- 
matic records could be obtained of deflections of not less 
than 5 mm. A Nernst lamp was used in this case. 



Adams, 52 
Aldebaran, 95 
Ami des Aveugles, 141 
Arrhenius, 108 
Audion, 155 
Ayrton, 37 

Bacon, Admiral, 127 
Baker, Thorne, 81 
Bakewell, 75 
Balfour, Lord, 72 
Barr and Stroud, 37, 127, 129, 137 
Belin, 81 

Bell, Graham, 36, 39, 43, 147 
Berglund, 155 
Berndt, 47, 52 
Berzelius, 32, 36 
Bidwell, Shelford, 39, 46, 63, 66 
Biltz, 47 

Bodman, Mrs. E. C., 145 
Braille, 113, 123 
Braille Review, 112 
British Association, 104, 145 
British Scientific Products Ex- 
hibition, 125 
Broadcast pictures, 77 
Brown, S. G., 67, 109 
Brown, W. Forster, 5, 122 
Browne, F. C., 37, 47, 114, 116 

Caselli, 76 

Clausen, 66 

Code pictures, 77 

Condenser, 22 

Conductivity, 48 

Contrast, perception of, 59 

Conversion of light into sound, 89 

Curie, Mme, 108 

Current, electric, 22 

Daily Chronicle, 101 
Daily Mail, 65 
Daily News, 99 
D'Arlincourt, 76 
Dawn, 68 

De Forest, 37, 155 
Drude, 47 

Edison, 65, 154 

Electrician, 103 

Electrons, 14 

Ether, 26 

Exploring Optophone, 97 

Fisher, Lord, 70 
Fizeau, 36 
Fritts, 40 

Gramma rays, 17 

Giltay, 37 

Green, Miss M., 137, 141 

Gregory, Sir Richard, 125 

GrindeU Matthews, 37, 68, 155 

Hesehus, 37, 47 
Hittorf, 36 

Illumination, 55 
Illustrated London News, 125 
Induction, 21 
lonisation, 19, 47 

Jameson, Miss, 125, 127, 144 
Joule's law, 24 

Kalischer, 37 
Korn, 37, 80 

Lancet, 119 

Law of light action, 61 




laesegang, 40 1 

Light, 17, 61 

Lodge, Sir Oliver, 7, 95, 108 

Lucas, 37 

Lux, 55 

McCarthy, G. P,, 137 

Magnetism., 27 

Marc, 47 

Matthiessen, 36 

Medical Supply Association, 123 

Mercadier, 37, 39 

Metre candle, 55 

Minchin, 37, 40, 52 

Morning Post, 131 

Moser, 46 

National Institute for the Blind, 

117, 145 
New York Sun, 99 

Ohm's Law, 24 
Optical Instruments, 84 
Optophone, 94 

black-sounding, 131 

exploring, 97 

reading, 105 

type-reading, 111 

Pantelegraph, 76 
Parsons, Sir G., 139 
Pearson, Sir A., 118, 125, 133 
Perry, 37 
Pfund, 47 
Phonoptikon, 114 
Photoelectricity, 31 
Photographophone, 154 
Photophone, 63, 148, 151 
Picture transmission, 75 
Pintsch's control, 67 
Presser, 41 
Prince of Wales, 136 
Protons, 14 
Punch, 127 

Quantum theory, 29 
Quincke, 29, 36 

Rankine, Prof., 37, 149 

Recombination of ions, 51 

Regnault, 36 

Relay experiments, 63 

Riecke, 47 

Ries, 37 

Riess, 36 

Righi, 40 

Rontgen Society, 117 

Rosse, 52 

Royal Society, 109 

Royal Society of Arts, 137 

Ruhmer, 37, 40, 81, 149 

Sabine, 36, 40 

St. Dunstan's Magazine, 144 

Sale, 46 

Scientific American, 114 

Selene, 13 

Selenium cells, 38 

Selenium, properties of, 31, 32, 38 

Siemens, 36, 47 

Smith, Willoughby, 34, 36 

Stainsby, 138, 144 

Star, 135 

Star transits, 160 

Stark, 47 

Sullivan, 67 

Swinton, A. A. Campbell, 137 

Synchronised pictures, 80 

Talking film, 159 
Telescope, 84 
Television, 82 
Telewriter, 77 
Thomson, Sir J. J., 47 
Times, 120 
Tonoscope, 93 
Truth, 120 

Ultra-violet, 60 

Wave-length, 28 
Westminster Gazette, 121 
Weston, 67 

X-rays, 17, 60 

Printed m Great Britain &y Eazell, Watson A Viney, Ld., 
London and Aylesbury.